The bottom recess will fit a single 8x3mm magnet. I'd recommend printing with PETG if possible (less brittle). The original model was designed for assembly as opposed to print-in-place. Printing the parts separately will likely yield better results. To assemble, I've found it easiest to align the front edge (latch side) of both sides of the case. Once those are coupled, you should be able to press the hinges into place.

UPDATE: Models with looser tolerances on the hinges have been added. If your printer is not well tuned, I'd recommend using those instead.