I can only speak personally, but I have a 6 x 4 garden shed as my chicken house, with 4 nest boxes about 2 ft off the floor at the back. When one of my hens goes broody, they generally fart about for about 3 to 5 days, and move from box to box. I'm collecting eggs every day so I disturb them aswell. The best way I can tell if a hen will sit tight is if she still hunkers down with no eggs under her. I make sure she's sat for 3 days, then move her with the selected eggs to another garden shed that has a nest box on the floor, same size as the laying boxes 12 x 12 inches.
They are nothing spesh