I originally designed and Ken and I built this to feed fermented feed. Although we realized that FF wasn't going to work well for us, the feeder stayed up and we used it for their All Flock. (I've also used Grower/starter if my feed store was out of All Flock with great success) This feeder looks funny, but it's easy to build and my 22 birds did very well with it. We put a brick at one end for the bantams and Silkies, but there was plenty of room at the feeder, they didn't tromp in or on it, they didn't bill food out as badly because it was more difficult for them to do that, and a lot of them could feed at one time. The top was slippery, so they couldn't perch on top. I hope this helps you...
https://www.backyardchickens.com/articles/fuss-free-fermented-feed-feeder.67818/