My super easy keeper started chewing wood when he went on his diet. I got him a nylon webbing slow feeder by Derby that is safe to put on the ground if your horse doesn’t have shoes. That helped a lot because he could flip it over to keep looking for the “good part”, which slowed him down and kept him busy. Also when he could still afford the calories, a lik-a-ball with alfalfa pellets kept him busy for a good 2 hours. But when the feed consultant assessed his condition and pointed out that you can only feel his ribs “with a running start”, that bit of fun ended. He isn’t interested in any toy that doesn’t dispense food - except whatever blanket he can snatch off his rack and then that’s super entertaining to shred.
Once he got out of the habit of wood chewing, I put his webbing slow feeder on a hay hoop. It’s probably less fun for him since he can’t flip it over, but it’s much easier to fill and close. He seems to be ok with it since his stall is still standing.