What did yall do for your toddler to stay in bed in the morning?

We are just starting big boy bed today! And he took his nap and got up about 2 hours later which is normal and then came out of his room. Like opened the door and came out. I dont mind that during naps. But I dont want that during night time. And I dont want to put a child lock on the door and "lock him in" any suggestions?