Here is a modular deck box. The clasp, and dice tray are used to keep the boulder from rotating out, but this also allows for easy swaps between decks. There is also a bigger version on my page that holds two of these boulders. It uses 8, 5mm diameter magnets and is fairly sturdy for the build and magnets used, also can store the upper half of the boulder and the dice tray as shown in the pictures.