Mine that I built were gravity feeders. I made them out of plywood. They were about 2 feet wide and 1.5 ft front to back and about 2.5 ft tall. You basically make a box of of plywood and on the inside you make a ramp going from the back wall of the feeder to the feed opening which was about 1.5 inches tall and ran the width of the feeder. Make you a box out of 2x4s laid on edge around the opening that comes out past the feed opening about 3 inches. Cut one strip of 2x4 wire fence and staple it over the opening in the feed trough. The chickens have to stick their heads down through the fencing to get the feed and can't sling their heads sideways to throw the feed out on the ground.