Hi there Slushy, welcome to the forum
:wave:
LiamP has given good advice. Bunnies are really quite intelligent and most pick up litter training quickly. If he already has a corner he poops in, put the tray there, as if he has decided on a spot you don't want to confuse him by changing it. Any wees can be soaked up with kitchen roll or tissue and stuck in there too. Don't tell him off for any accidents as bunnies just do not understand. Much better is to give him a reward when he goes into the tray, a pellet or a sliver of food, as he will associate the tray with delicious noms.
People use different things for their litter trays. The cheapest is shredded newspaper with a big chunk of hay on top, as lots of bunnies like to eat hay while they poop (goodness knows why :lol
. Some people use something called megazorb instead of newspaper, which is paper pulp, and others use compressed wooden pellets, my personal favourite as they are very absorbent. Keeping the tray nice and clean will encourage Slushy to go to it often.
Is Slushy neutered? If not, that may be why he is leaving droppings everywhere when he gets out, he is marking his territory. Neutering prevents this, and also stops hormonal behaviour like spraying, honking and aggression when his hormones kick in, assuming he is a young bunny.
If you struggle to get him litter trained you can always pop back and ask questions.