This is a remix from @doc 's design: https://www.thingiverse.com/thing:2815022

I trimmed the back plate little slimmer, and made screw holes to fit Biltema perboard. I printed this with 4 walls and 4 bottom and top layers. Infill 10% is enough and this comes plenty strong even if printed back towards the buildplate. It would be even stronger if printed 90 degrees in different orientation so that layers lines would go against the strain, but seems like 4 walls makes it strong enough even this way.

Biltema pegboard holes are 4mm wide and 12mm abart from each other and it is sold in Scandinavia, but there are other brands around the world with same diameters. You can also attach this to any wood surface with wood screws.