When printing soft or flexible filaments, even the slightest resistance in the spool holder can cause unpredictable tension/stretching in the filament feed, leading to irregular prints. This spool holder for the Prusa MK3 frame uses a single 608 bearing to minimize feed resistance.
Only the "hat" requires supports - the other parts can be printed on their sides.
Drop the bearing into the hat & push down firmly to seat. Drop an M8 nut into the bottom of the axis & get it close to seated, then insert an M8 screw thru the top of the bearing/hat assembly & screw it into the nut until firm. Give it a test spin. Giggle and spin it again. Hook it onto the frame, hook the guide on next to it, then drop a roll of filament onto it.