When I was bonding mine I was so paranoid that I set up a nanny cam when I had to leave the apartment for a class. I was gone for 2 hours but I checked the cam every 15 minutes or so. But even if something happened I wouldn’t be able to do anything about it because I was far so really I was just being weird. Many people describing instinctually knowing when you can leave you bunnies alone.
I found that the smaller area I gave my bunnies, the less they were likely to fight so if I had to leave for a while I’d usually put them in a litter box sized pen, put a small bowl of water in it and leave them. I gradually increased this. They still had scuffles but they never got bad. When I put them in a larger pen for the night and I slept next to it they also didn’t fight or draw blood so I figured if I were gone for a while they hopefully wouldn’t do anything too rash. My bunnies never drew blood, if your bunnies have a good track record then you’ll have to make the decision for yourself whether you are okay leaving them together. If they fight often then I’d discourage it but like I said, use your own discretion.
It probably wouldn’t destroy the process if you kept them close together but separated by a small gate or something if you really are afraid of leaving them together. Also small scuffles aren’t ground-breaking, my bunnies still break into little scuffles and once in a blue moon I’ll find a tuft of fur.