I remixed JamieLaing's great model of a hand to be used as a shelf.
To achieve that I removed the base, rotated the hand so that a plate or board can rest on the fingers and palms and put two hidden screw holes on the "back" of the hand.
You have to print the hand two times and flip it once to get both to hold the shelf.
Printer brand: Creality
Printer: Ender 3
Filament brand: 3djake ecoPLA
Filament color: White
Filament material: PLA
The model can be printed without supports (the only part with overhangs are the screw holes and that can be bridged. If you have problems with bridging enable supports touching the buildplate for those).
I printed with 15% infill in PLA which I think is enough for this model.
Printing time is around 9.5 hours per hand on an Ender 3 (with 50mm/s print speed) and it uses about 85g of filament.
I had to first remove the base in Meshmixer, because it had just a bit more then 300k vertices.
Then I imported the model into tinkercad, scaled it up, rotated it, removed the part that would be "in the wall" after the rotation and then I added the screw holes.