I want to build a double 10 inch box that fits under the back seat of my 2002 sierra extended cab. I know they are available to purchase, but I want to build it myself using 1" MDF. all others seem to be sub-par. It is not my first box. I am hoping someone out there can get me started with the outside dimensions-specifically , the size and angles necessary for the two side pieces.

 

Since this isnt your first box, you should just be able to take a measuring tape and measure the heights and cut out your pieces. Measure at the back, then measure at the front that will give you your two points, draw the line and theres your angle