I saw someone post elsewhere of a similar project they crafted out of wood and have been mulling the idea over for a few weeks, so I unfortunately couldn't find them to cite with the original idea.
It is designed to hold a decent set of dice (i think it should hold 7 standard dice with ease, maybe 8 depending on size). It also has a rather large cavity for storage of other things: 17.5 cm x 11.7 cm x 26 cm - large enough to hold some pens/pencils, maybe a small notebook, folded character sheet, or even a 1 inch mini should fit.
It unfolds into a dice tray - I would advise lining it with some felt or leather if you intend to roll some heavy metal dice - and a liner might make a mini a tight fit inside.
The whole thing is designed to be held together by magnets that are imbedded during the printing process. The magnets I have are 5mm diameter and 1 mm thick neodymium, I have 8 placed around the perimeter of the main part, and 4 more to hold on the side lid which should be enough, although I won't know until I print it.
For embedding the magnets, you'll need to use your slicer's ability to "pause at z" and embed the magnets. MAKE SURE THAT YOU ORIENT THEM CORRECTLY. I would advise that you put all of the magnets in one side with the North facing outward, print the other side and embed them with the south facing outward. The side lid will need two norths and two souths - paired along the long side - if you follow these instructions.
Side walls are all in increments of 0.4 for easy printing, and top/bottoms are 0.6 minimum - so layer heights compatible with that are ideal (0.12 and 0.2 will work wonderfully).
Make sure to use at least 2 walls - although I hope that's obvious. Print the main body in the orientation it is saved in. Make sure to set up two "pause at Z" commands using your slicer just before it covers up the holes where the magnets will be embedded. One pause will be for the sideways magnets to connect the side lid, the other pause will be for the rest of the magnets that will connect the two main body segments. Make sure to orient your magnets all the same on one part and then opposite on the other so they will attract - digging them out won't really be an option if you mess up.
Pause at Z Heights:
Pause 1 - Just before 8 mm - to embed the vertical magnets for connecting the side lid - When sliced at 0.2 mm this is layer 40, When sliced at 0.12 it is layer 66
Pause 2 - Just before 13.4 mm - to embed the 8 magnets to secure the main bodies together - when sliced at 0.2 mm this is layer 67, When sliced at 0.12 it is layer 111
The side lid will need to be rotated 90 degrees from its saved orientation, so that the large face is flat on the print bed. You'll need to use another "pause at Z" command just before the magnet holes are covered up to embed them again. How you orient them depends on how you oriented the sideways embedded magnets in the main body.
Pause at Z Height: Just before 8.4 mm - embed matching how you did in your first embedded magnets in the main body. - when sliced at 0.2 mm this is layer 42, when sliced at 0.12 it is layer 69 heh