I have a hay net that is tied down inside a barrel for my horse. It seems to work fairly well.
Hondo is fed hay using something similar but using a plastic water trough about twice as long as a barrel. The net openings are just large enough for Hondo to get his lips and teeth into. He of course tries to then lift the entire flake out but only gets a bite as it is tied through the drain hole. There is a clip on the bottom of the net used for fastening it. The net is filled in the feed room and carried to the trough.
The alfalfa leaves that are broken loose when he is working on the flake fall to the bottom of the trough where he eats them without eating off the dirt (or mud). Works good.
Different hay probably needs different opening sizes. I have one small mesh that he can't get anything out of with the alfalfa hay being used.