Store Copic markers on their side to avoid drying out one side. Works best if it can sit against a wall or desk. I used a higher infill for the base so it wouldn't move around as much when you pull out a marker. 

You'll need to print the top and the base and at least 2 of the pillars. I went with 4 but the markers are light enough you could get away with two diagonally opposite each other. I'm sure there is a better way to design it but it worked for my needs.

If folks show interest I'll do a redesign.