Wall-Hanger(Ø20mm) for Ø4,5mm screws

Just drill a 10mm deep hole with a Ø20mm forstner bit and glue it into you object(the small slot facing up). After that you have to install a Ø4,5mm screrw with a dowel into your wall.
Finally, you only need to hang your object on the screw by sticking the screw in the big hole and pulling the object slightly downwards.