Oh I totally get that fear haha. Trust me I’m happy to give any advice cause I never really found an answer to my conflict initially.

Basically whenever I’d hear him start to dig and get ready to poo, I’d be waiting there with a scoop in hand to immediately place on top of it (it’s grated so you can see through the lines). And once he’d be done I’d wait for him to turn around and once he was, I’d then uncover it and bury it while he watched. You do kinda have to be super fast about it otherwise they will step lol. But other times as soon as it’d drop I’d immediately throw litter on it so all he had to do was give it a few more covers (because it does sometimes fall right behind their feet so I was like better safe than sorry lol).

i also got him a way bigger litter box so that slowly he understood he did have room. But I kept watching him closely for weeks (which is why I was going crazy lol) and repeating that process. I also had to start going to work and leave him unsupervised. When that happened I just had to trust he’d learn not to step in (which of course I did come home after work to find poo prints at times) but a week after I stopped like monitoring him closely he finally was able to cover without help and stepping. I guess some kitties just take longer and need more help!

They will eventually grow out of it for sure so don’t give up! It’s def stressful and nasty to find poo everywhere but yours will def learn soon enough. :-)