People manage broodies in different ways, so there are different ways to make it work. Some leave them with the flock 100%. For me, since I have several roosters, I move a broody as soon as she starts to sit, as soon as I'm sure she's committed. I have a nursery run that is parallel to my main run. My broody gets a large dog crate that is open all the time so she has access to the nursery run when ever she wants during daylight hours, but does not have to deal with intruders. Everybody can see everybody all the time, but no one can bother her. Her crate is actually in the closed run off the coop, with it's own door that can be secured at dusk, so she is safe from predators. This is my preferred method so my broodies don't get stressed and so the newly hatched are safe until they are old enough to get out of the way of the big birds. If you move a broody you have to make sure she can't get back to her original nest, or she will try to go back. That's why I do it early on, if she's been sitting more than a few days, I would not try to move her.