This a magnetically sealed case I made for my Chaos Dice (https://www.thingiverse.com/thing:3058094).
It uses a total of ten 3mm cube magnets. Five per side. I used a tiny dab of superglue on the bottom side of each magnet to lock them in place. If you don't they will pop right out when the extruder passes over them. You must make sure before you have all the polarities matched up so the case can be sealed from any position. Because once you glue them in place they are not coming out. Also make sure you know how to pause a print because it'll take you a minute or two to get them all in and a few seconds are needed to dry before you start the print back up. My set was printed on a Prusa i3 MK3 so I used slic3r and dropped the gcode in ColorPrint (https://www.prusaprinters.org/color-print/) Very easy to use.
I tried Colorfabb Bronzefill for the case but the detail of the top of the case was too hard to nail just right so I used Hatchbox Copper PLA. It goes very well with the Bronzefill dice that are 14 hour tumbled using my KitchenAid Rock Tumbler (https://www.thingiverse.com/thing:3108867)