A more typical way to do this would be to instead cut the front/back and sides from a board, then use a piece of plywood in rabbets as a bottom.
The easiest way to do this is as a file which has one side, and a front/back part and which is cut twice — drawing it up in Carbide Create we get the dimensions:
which are easily transferred into a file for OpenSCAD Graph Editor which implements this style of joinery:
and when we add the dimension for the position separating the two parts:
We get:
which yields a couple of files which can be imported into Carbide Create.