I always struggled to efficiently hold and use the bigger 0.5 lbs spools of string material... So i created a quick holder for the 2 common spool-sizes (0.5 and 0.25 lbs).
Only other thing needed is a countersunk M3 x 20mm-screw.

The "nail" is only needed if you print the rods as 2x half to avoid large support structures. Then it is used to be pushed in the back and lock together the 2 halfes...
But also a dab of glue fixes them together easy.

Best in PETG.