As requested by a Reddit user.

You will need a wooden cylinder (20 mm in diameter) and 4 self-tapping M3 screws at least 35 mm long. Fitting dowels are required for the wall holes (unless your wall is made of wood).

Inspired by elbow design's APIO coat hanger, which seems to be (at least partially) inspired by Attach coat hook by Dimitri Bähler.

To support elbow design and save a considerable amount of time please consider buying a ready-made kit at elbowdesign.dk.

Update: Here is a tutorial on this type of mount: https://www.instructables.com/How-to-Create-an-Elegant-Keyhole-style-Wall-Mount-/