I was using a bearing hub and a piece of threaded rod to hold a spool, but as my collection of PLA grew, it was too much weight for the threaded rod and starting to use up all my 608 bearings.
The PLA Spools from Ultimachine are 1.5" in diameter. My local Home Depot sells 10' long sticks of conduit for $12 and they cut it for free. (I went with 3', 3', 4'). The conduit fits nicely in the spools and they spin fine. There is a bit of friction which isn't a bad thing IMO, so the spools don't unwind too much accidentally.
I have some slat-wall brackets that seem to work well, keeping the spools at a distance from the wall without letting them fall off the wall.
NOTE: The measurements of the conduit at Home Depot is listed by inner diameter. 1.5" Conduit is too big - 1.25" Conduit fits well
1 Go to Home Depot.
2 Pick up 10' Conduit (1.25" Inner Diameter) from the Electrical Dept.
3 Try not to hit anyone.
4 Ask someone in an orange apron to cut it for you (optional).
5 Pay and hook it up.