I remixed Spooner2011's finger hook (thanks Spooner!) to fix up the manifold errors (overlapping objects) which were giving me problems slicing with KISSlicer, plus I added some wall-mountable screw slots for a sturdy way of fixing it to the wall.
See my new derivative that eliminates the base completely while still being screw mountable!
Screw 2x screws centres 40mm apart into the wall, door, etc, where you wish to mount the hook, leaving about 2mm below the screw-head sticking out.
Slot the hook over the heads, and slide down to lock in place.