Tension Nut Filament Guide

Try https://www.thingiverse.com/thing:737197 for a version with a flange.

I added a filament guide, based on my tension nut, so I don't need to worry about the filament looping off the roll on a long unattended print job. The tension nut is tight enough that it doesn't need a screw to hold it in place though you can add one if you need it.

The hole has a large fillet on both sides so the filament will pass through easily and the arm should accommodate various spools.

You can add a small square of foam in front of it and push the filament through. The foam will clean off any loose dust or particles on the filament before it gets to your extruder.