I sandwiched 3/8" plywood - smooth sides in... and 2 4' x 10' aluminum sheets into one stack of materials. I then mapped out the exterior profile including door location on the side, and cut it all out.

I then removed the aluminum and mapped out all the interior bulkhead locations and cabinets. I drilled small holes in the corners of all component locations in order to transfer the drawings to the opposite wall.
Fabricating the sides