Just realized that I put the bottom board upside down, and putting the entrance reducer in has raised the box off the board. This is day one for me. Would it be okay for me to take the box off the board for the few seconds it'll take to turn the board over? I'd just put it on the ground real quick then pick it back up. Or would this cause major disruption to my new bees?
go for it. if you have an empty super, set it on that. otherwise, just do it.
it is unlikely that your queen would exit onto the grass, but watch for a cluster on the ground after you do this just in case.....
You could also take off and turn your outer cover upside down, keep your inner cover on, and put the hive on top of it while you swap the board around. If you're worried about bees coming out of the inner cover, put a piece of plywood over top of the hole.