Anybody with experience building hoppers for square items?

I am building a hopper for 6mm square nuts. I need to them to come out the bottom of the hopper oriented vertically. The size of the square nuts is 10mm x 10mm x 4.6mm. My main question does anybody what angles are best on the sides of the hopper to be in order to reduce them from stacking up and "clogging" near the bottom. My best guess is steep but wanted to know if anybody had experience.