This was based on a post from Reddit user u/LemonStream so credit where credit is due.
I tried to adjust it and hopefully it will print in place.
You will need 16 5mmx2mm magnets to allow everything to attach.
You only need to print 1 of the Pen tray but 2 of the Dice Tray will be required.
I will leave this as a work in progress until I can confirm that it can be printed correctly.
The symbol is my Bat Country Customs logo.
Update: Added Pen Tray v2 which increases thickness of pen tray lid so printing will be more reliable but shouldn't interfere when closing.