This was the hardest part. I built it in two pieces, the base which is made fom 1x8 and is the frame and support for it, and the plywood top. I had to put the plywood piece in first and put over the front seats I then put the frame in and wired everything. Finally I was able to lay the plywood on and screw it down.

 

oh so the bottom of the box is just the floor?

 

Yeah, the section with the sub and compressor is the only part which has a floor. My carpet in the back is pretty stained so I figured that I didn't need to protect it.