Try to keep an eye when he poops in his litter box and give him a pellet/treat when you see him sitting on it. Poops aren’t that bad because they’re dry, so just pick it up and put it back in the litter box. As long as he’s not peeing, it’s not so bad.
And yeah, agree with the no punishing. They respond well to positive reinforcement I think, at least my bun does. If he tries to go somewhere I don’t want him to go, I say his name kind of strongly he either turns back or keeps going. If he turns back, I reward him. If he goes back, I move him away. If I move him away a couple times, he most of the time gives up, and if he does, I give him a pellet.
They’re very VERY motivated by food. My bun will sometimes pretend he’s peeing and watch me, waiting for me to say “good bunny” and run at me for a treat. You can tell by the demeanor if it’s real or if it’s just a treat.
Anyway thats just my story. Good luck! and don’t fret too much about poops. Just keep hand sanitizer around and pick up the poops when you find them until you can get him neutered!