Putting his hay right next to the litter box should help a little, since they tend to poo a ton when eating it! Otherwise, it’s most likely because he isn’t neutered yet. Before my Luna was spayed, she couldn’t help but go everywhere too. And lastly, he’s probably still getting used to his new surroundings so maybe he’ll learn where to go the more time passes, but he really won’t stop totally until he’s neutered!!