I think i figured out a way to make the case look reasonably professional and relatively easy to make. I'm gonna order two polyethylene 'plates' with a 3mm thickness with the correct dimensions, glue 4 of those threaded posts in the corner and glue a metal or plastic strip around the edge. This way i'll have a removable top part to access the electronics.

Something like this (Note: dimensions are not to scale, AT ALL) :