Listed below are the step by step instructions for building the Impala trunk boxes.

1. Assemble required tools (see tools req'd)   
2. Assemble all the material req'd (see material req'd)
3. Empty the Trunk and protect fenders & bumper. You will be getting in & out of the trunk often while making the templates and then fitting & installing the finished panels.
4. Next take a sheet of the foam board and cut to the approximate shape of side door trunk panel. Leave enough material for trimming to the finished panel size.
5. Place the board against the driver side trunk rail and trace the outline of the floor, wheel hump and taillight covering. (If you look carefully you'll notice the area above the taillight cover is slightly different on the drivers side. At least on my car it was).
6. Remove foam board and carefully cut along the traced line with the razor knife. (I recommend doing this on a solid work surface not in the trunk).
7. Continue tracing & trimming until you have a perfect fit. This is a time consuming process but will save you money in the long run.
8. When you have a perfect fit you can trace the outline of the template onto the MDF or Plywood. You only have to trace onto one panel since you will clamp two panels together when you cut out the pattern. This will give you 2 identical panels and save you some time.
9. Before cutting the pattern measure the location of the door from the bottom of the panel. The door opening should be approx 10" high x 14" long. Use a square to make the sides of the door perpendicular to the bottom. When you have marked the door location clamp the 2 MDF/Plywood panels together carefully aligning the sides. Leave the panels clamped together for the next step.
10. Now that you have the panels cut it is time to cut out the door openings you laid out in step 9. Begin by drilling a 1/4" hole at opposite  corners of the door. Next using the Saber saw cut out the opening being careful to follow the lines. These edges will be clearly visible when the panels are completed so some extra care here will result in professional look when your finished.  Use a straight edge and more clamps if you have to. KEEP THE DOOR CUTOUTS. THEY WILL BECOME THE DOORS.
11. Next smooth all the outside edges and test fit the panels. When the panels fit properly use a spring clamp to hold them in place against the drip rail. Now reach thru the door opening and using a black marking pen trace the bottom edge of the drip rail onto the back of the panel. You will use this line as a guide for mounting the panel mounting spacers.
12. Remove the panels and place them on your work surface back side up. Measure 1/2" down from the trace line at 2 locations. Next clamp the 3/4" x 1" x 14" hardwood spacer along this line. Drill 4 pilot holes for the #10 wood screws. Attach the spacers with 4 #10 wood screws and remove the clamps.
13. The (2) 1/4" carriage  bolts are installed next.  Measure the location of the two bolts on the front of the panel. The heads of the carriage bolts have to be counter sunk so you have to first drill a 3/4" diameter x 3/16" deep hole using a wood boring bit  then drill the 1/4" hole for the bolt. Now you can insert the bolts thru the hole and place a flat washer and nut on the back and tighten until the bolt head is pulled into the hole.
14. Next locate the 1" x 2" X 12" hinge mounting plate. Clamp this to the back of the panel on the end you want the door to hinge from. Mark the 3 screw locations and drill the pilot holes for the #10 x 1/12" wood screws. Attach the mounting plate with the screws and remove the clamps.
15. Bring the panels and the 3/4" x 3" metal 'L' brackets to the trunk. Remove the lower cargo net hold down hooks and place the 'L' bracket over the stud used for the hook. Clamp  the panel into position and reach thru the door opening and mark the location of the 'L' bracket against the back of the panel. Remove the panel and attach the 'L' bracket to the back of the panel.
16. The next step is to attach the doors. This step requires great care to center the panel in the opening since any mistakes will be highly visible when the finish material is in place. Place the door panel in the opening and using equally spaced shims center the panel. Place the hinges on the door and against the mounting bracket. Mark the location of the screw holes. Drill the holes and attach the hinges with the supplied screws.  You may have to remove a small amount of material from the sides of the door to allow for the thickness of the finish material.
17. Install the panels and check for fit. If everything is to your satisfaction take a break and prepare for the next phase, making the trunk hinge panels.
18. The procedure for making the trunk hinge panels is a little easier than the side panels but still  requires care and patients if you want the finished product to look good .
19. Cut a piece of foam board or cardboard 18" x 24". If you have removed the side door panels you will have to re-install them for this next step. Place the foam board against the hinge bracket butting it up against the side door panel. Using the compass trace the outline of the floor and wheel hump onto the foam board and  mark where the opening for the trunk hinge will be.  On your work surface cut along the lines you traced then test fit the panel. Repeat  until your panel fits perfectly. Make sure you cut the slot for the trunk hinge deep enough so there is no interference when the trunk is closed.
20. Now that your template fits the way you want it  trace the pattern onto the MDF or Plywood and cut out with the saber saw. Bevel the back edge of the hinge panel where it contacts the floor and the wheel hump at approximately 45 degrees. Smooth the edges and place the panel in position.
21. With the panel held in place reach behind and trace the outline of the trunk hinge mounting bracket slots onto the back of the panel. This is where the panel will be attached with the carriage bolt.
22. Remove the panel and mark the center of the slot. Drill a small 1/16" pilot hole to mark the location on the front side of the panel.
23. Using the same procedure you used to drill the hole for the carriage bolt in the side door panels drill the counter sink for the head and then drill the hole for the bolt.
24. Next mount the panel and fasten in place using the the carriage bolt flat washer and wing nut. If everything is to your satisfaction get the marking pen and trace a line on the side door panel where the hinge panel buts against it. If you can reach behind the hinge panel trace the backside also since this will be the guide line for the bracket.
25. Remove the hinge panels and the side door panels. On the work bench clamp the  mounting bracket onto the side door panel 1/2" ,or the thickness of the hinge panel, from the front line or even with the back line and install the bracket. Test fit the panels. If all is ok then proceed to the next step.
26. Next make the rear seat back panel. Using the 1/4" plywood cut it to fit the seat back bracing area. You will have to notch it to clear the wheel humps and also the wires on the rear deck. When you have the fit right mark the rear seat bracing pattern on the back of the panel so you will know where to mount the spacer where the panel will be bolted to the seat bracing. 1 in the middle and 1 on each end. Remove the panel and attach the spacers the reinstall the panel and attach it to the seat bracing. You will need this in place when you make the template for the rear side panels.
27. Re-install the hinge panels and the side door panels and trace the pattern for the rear side panels. This will take some time and great care since you have to make clearance for the torsion bars and the speakers plus make the angle where it buts against the rear seat panel and the contour where it meets the floor and wheel hump. If you are thinking about replacing the stock speakers with after market speakers you will have to make the clearance around the speaker area deeper to compensate for the larger frames. When you have the pattern just right trace it on to the 1/2" MDF or Plywood and cut it out. Once it is cut out smooth the edges and bevel the back of the bottom edge to 45 degrees where it meets the wheel hump. When you have the fit the way you want it square it to the hinge panel and mark the rear seat panel where the 2 panels meet. This will give you the location for the mounting brace. Repeat for the other side.
28. With the rear side panels cut to fit remove them and the hinge & rear seat panels. Next install the mounting brackets for the rear side panels on the hinge panel and the rear seat panel using the marks you made during the trial fit. Mount the brackets 1/2" in from the line you made on the rear panel and 1/2" from the edge of the hinge panel using the wood screws and glue. next re-install the panels and mark 2 locations at the front and rear of the side panels for the bolts that will hold them together. Make a mating mark on the rear seat panel and the hinge panel. You can drill the pilot hole on the front edge will it is installed in the car but there isn't enough clearance to drill the back ones in the car.
29. Take the panels out of the trunk. Using the Forstner bit that will give you enough clearance to countersink the head of the mounting bolt plus the thickness of the fabric you are using  drill the recess using the pilot hole you made. Only go deep enough to recess the bolt head. Next drill the holes for the bolt shaft. If you use 1/4" bolts use a 5/16" drill bit so you have some clearance. Next drill the holes in the mounting brackets for the special nuts you have to use with the bolts. You will have to make this hole undersize so it holds the nut in place. Check the directions on the package. When you have all the holes drilled and the nuts inserted assemble the panels to make sure they bolt together without any problems. You can do this on the bench if you're tired of climbing in and out of the trunk. Take a break you probably need it. 
30. Now it's time to put the fabric on the panels. First mark each panel and the doors with the side of the trunk they go on and with the word "BACK" on the side that will not be covered with material. This is particularly important for the doors so you can match them to the correct panel and in the correct orientation. You will need a clean open area to layout and cut the fabric.
31. Spread your fabric on your clean surface with the good side down and smooth out the wrinkles and creases. Place the panels on the fabric with the back facing you. Using the marker trace the outline of the panel onto the fabric but do not remove the panel. Make yourself a 1-1/2" spacer so you can trace the panel outline that much from the outline. You will wrap this material around the edges and onto the back of the panel. The outlines will help you line up the panel and the fabric once you have applied the adhesive. When you have all the panels marked cut the fabric on the outer lines and label the fabric to match the panel it goes with.
32. With the fabric cut to shape it is time to glue it to the panels. DO NOT glue the fabric to the doors at this time just the panels. Lay the fabric with the back side up and the panel with the back side down and spray a thin coat of adhesive on both surfaces and let it set up for 5-10 minutes. Now is the time to insert the carriage bolts into the side door panels and the hinge panels and secure them with the washer and wing nuts since they will be concealed behind the fabric. Do not install the bolts for the rear side panels since they are put in during final assembly. Once the glue has set carefully place the panel on the fabric staying within the guide lines. If everything lines up press down on the panel to set it then turn it over and smooth out any wrinkles. DO NOT cut the door openings yet. Next spray a 1-1/2" wide band of  adhesive on the back side of the panel and let it set then wrap the material around the edges and onto the back. Trim off the fabric that bunches up in the corners or curves.
33. Next spray the back side of the door opening and the door with the flat black paint. With the paint dry make a diagonal cut from one corner to the other in the opening then spray the adhesive on both surfaces let it set then wrap the material around the edges and trim off the excess.
34. With all the panels covered with fabric it is time to work on the doors. Place the bare doors into the proper openings lining up the marks you made previously. Place some scrap fabric in the gaps between the panel and the door and check for tightness. If the door is to tight then you will have to trim 2 sides of the door slightly until it fits without getting stuck. Make sure you follow the contour of the door and only remove a little at a time. Once you have the right fit glue the fabric to the door like you did on the other panels. If you are not going to cover the back of the door with fabric you may want to paint it before putting on the fabric.
35. Now that you have all the panels covered it is time to assemble the doors and install the panels in the trunk. Place the doors in the openings and mount the hinges. Next install the side door panels in the trunk clamping them to the back of the drip rails using the carriage bolts that were installed in the panel earlier. Next install the hinge panel using the installed carriage bolt to clamp it to the hinge mount and the bolting it to the side door panel using the right angle bracket. Next install the rear seat panel but don't bolt it to the frame yet. With the rear seat panel in place install the rear side panel using the bronze furniture bolts. If you didn't properly align the holes earlier this will be a little difficult. When you have the side panels in and secure you can bolt the rear seat panel in place and re-install the rear seats.
36. That's it. Get yourself some refreshments and admire your work then go show off to your buddies.