My most recent project was building new hay feeders. My old one the horses had pushed and pulled and broke every screw. It was leaning so crooked I’m surprised it didn’t blow over. I disassembled the old one and rebuilt it. I built one hay feeder for the front pasture and one for the back.
If you decide to make one make sure you don’t make the front too tall for your tailgate to come down, and the sides need to be about even with/below the horses chest. If you build the sides too tall the horses push on the walls to reach the hay on the bottom when it gets low.
Here are pictures