I only went through one broody hatching episode, and I did not isolate her. It worked out OK as she was the top hen and could do what she wanted. I had hoped this would make it easier to integrate the chicks, but my lowest hen bullied them a bit so I had to watch out and pull her out when they were older and going to roost. And then for a long time I had chicks sleeping in a nest and getting them to roost took a long time! The other hens love my broody, though, so they got to hang with her 30 minutes a day when she was setting, and that was nice. Sorry, can't offer advice on isolating - but if I had done that, I would have put her in a dog crate in the garage, let her out once a day (you can kind of determine when her time of day is that she wants to pop out - mine did about 2-3 p.m.). I backyard free range and let her take the chicks outside to forage when she wanted to - I lost one out of 8 chicks to a flying predator - they are a breed good at hiding from predators.
In your other thread you said you didn't have much money to spend on it. You can buy hardware cloth and cut it into say 2'x2' pieces and fasten them together with zip ties for probably about $15. It doesn't need to have a wood frame or fancy little hinges & latches. Mez well do it now, long as you have chickens you will always need a cage for broody jail, brooder cage, sick pen, transportation or some kind of temporary housing.
