homedepot and lowes sell a sheet called whitewood, it is a hardwood with same characteristics of oak or birch but cheaper, i would build that out of mdf, but 2 3/4 sheets staggering the joints on each panel, lots of glue, and 3" decking screws (drywall screws **** and break) i would predrill every hole - counter sunk with a dab of glue on every screw (this helpd lube the screw not to split wood and then when glue dries is bonded together), my box for 16 -12's used 10 sheets of mdf, several 2 x 4's and gallon+ of tightbond, a bunch of carrage bolts, i would hate to have to remove it, sold van with box!