The construction is sure unconventional and I'm curious. So opinions, thoughts, and critique are welcome. This is a basic rectangular box without dadoes and rabbets but it may have reasonable structural stability and won't be subjected to much racking. The "X" in the back is half-lapped in the center so they're like locked scissors. A plywood back (1/4"-1/2") will be added and fastened with screws/nails if necessary (probably?).