D&D magnet bases I made for putting minis on. Some use 12 by 2 mm magnets from amazon the rest use 5 by 2 mm magnets.
Sizes include Tiny, Medium, Large, Huge, and Gargantuan included. For Small I use Medium as they still take up a 5-foot square and there was no good lay out for the magnets.
I just print with the holes facing up see picture of slicer, but it can be done with them facing down as well as long as your printer can handle small bridging.
V3 of the medium base is 2 small magnets v 4 has the option for either 2 small magnets or 1 large one.
As long as you are careful about lining up all the magnets you can print different colors and stack them to indicate allies and the like. I plan on eventually making it where there is a slightly larger version of each one that would allow the color to be seen easier from above.
The author marked this model as their own original creation.