I based the shape off of https://www.thingiverse.com/thing:2269715. The fact that their's has the forward angle forces the center of gravity towards the desk and thus keeps the hook on the table.

The issue I fixed with it is adding the rounded surface that the bag handle hangs from and also removed the angle that the lower "tail" had.

Personally, I add a thin layer of EVA craft foam, super glued onto the bottom of the portion that makes contact with the table, so as to prevent slippage and scratching.

I printed this with 3 layers at 1.5mm with 30% infill and it held up a 10lb backpack and barely had any popping sounds. Lay it on it's side in print setup and it won't require any supports. At least it didn't for me.