This filament filter is (to no ones surprise) heavily influensed by the great filament filter by CNC Kitchen, for the Prusa MK2S.
Put a small square piece of foam in the compartment, push through a pointy piece of filament several times to form a hole, snap it into place on top of the extruder and off you go.
Printed mine out of Prusa orange PETG
-Make sure the holes are clear after printing.
-Don't jam too much foam into the compartment. Otherwise the foam will grab or stick to the filament.
-Probably not a good idea to use with the filament sensors runout feature, since the filament that it pushes back up again most likely will get stuck in the foam.
-Start with putting the bottom end into the hexagonal hole, and then "lifting" it into place on top.