Update: Thanks to feedback from Tdub415, holes seen in Prusa Slicer have now been accounted for. the trays are about 1mm smaller, enough to ensure those gaps don't occur. The original file has been retained in case you want the slightly wider, but risk-of-slicing-issues, file.
This dice tray has been with me for many-a-session of D&D, and it handles all the dice I own beautifully. The shown example is printed at 0.2mm on a (rather poorly tuned) Ender 3 Pro.
I recommend lining the center with felt for maximum care of your dice. Plus, it's just nice!
Pictured are Dispel Dice Kickstarter rewards.
The author marked this model as their own original creation.