I've tried a few different holders for loose sample filaments, and so far this has worked the best.
This was a remix I made to enlarge the ring opening to fit over the end cap of single arm spool holders. I also re-did the holes to work with M3 bolts, since that's what I had available. Lastly, I designed some hub adapters to fit inside the rings. This keeps the arms from fully closing around the filament, or allowing the rubber bands to fall off when there's not enough tension from the filament.
I recently discovered https://www.thingiverse.com/thing:3036468 which works great with this using the following parameter changes in Fusion 360:
StandOffHeight from 150 to 160
LegDiameter from 20 to 18
SpoolWidth from 100 to 140
Update: I've added an appropriately sized STL of the one piece spool holder stand as well.
Nothing requires supports, they'll just need to be re-oriented.
The hubs are designed to fit snug, but I glued mine. If you have any elephant footing on the ring, you may need to debur it some.