ErgoDox keyboards have an unusual key layout, requiring additional 1.5u and 2u keycaps beyond the standard 100% keycap set. This tray keeps them all nicely organized and stacked. The trays friction fit together - but I recommend a rubber band for a little extra security. I've generated variants for SA, DSA, and DCS profile keycaps. The DSA isn't as deep, (8.5mm) so things don't rattle about. SA is 16.5mm deep and DCS is 10.5mm. Since SA & DCS have different heights, there should be some rattle, but nothing flipping over. 

The heights of the keycaps aren't necessarily standardized, so you may need to customize the height for your specific keycaps.
I've included Fusion 360 files and encourage remixing. (Please post it if you make a remix!)