@cornerstoneeg I shut the door. You can turn the doorknob so the lock is on the outside and lock it or you can put the babyproof plastic cover on the doorknob. My 4 yr old has a clock in her room and I set a timer on it for one hour. After that hour she can leave her room and she opens my son's door so he can leave.
I usually give a countdown like:
"We are going to do x for 10 more minutes and then it's time for room time."
"5 minutes until room time."
"Okay, it's time for room time! Would you like to bring a different book or toy today?"
We don't do electronic toys in general. We have a tv but we don't do tablets or anything with them.
I feel like during this time it's really good to allow them space to stretch their imagination. They have to come up with what to do for an hour. Sometimes my son just rolls around on the floor. Sometimes he looks at books or plays with a couple toys. My daughter is super into playing pretend so she has a castle in her room and she plays with little dolls with that. It's okay for them to be bored sometimes. I make sure that all wipes and diapers are out of reach so my son doesn't destroy those. He has a 6 drawer dresser and there's nothing in the bottom 3 drawers so he can't throw his clothes all around. We also still have a camera in there so I check in on what he's doing periodically.