Ok man umm first off you need some wood it all depends on what type of wood you want as long as it with-hold the weight then youre good. Once you have that (I hope you have the carpet that goes in your trunk) If you have the carpet make a stencil on the wood and cut it out. In order to get it to fit into your trunk you may have to make a CLEAN cut down the side(s). You may have to cut more from the wood because the carpet is never perfect with the shape of the trunk. You will end up putting it in and taking it back out to cut many times so dont get frustrated. once the shape is perfect with the trunk use 2 by 4s or 2 by 6s underneath the main base board. Here I made a diagram for you with instructions on how i did mine just go to this link:::
http://i905.photobucket.com/albums/a...G_0032-1-1.jpg