The best way to break a broody hen, is to put them into a "broody jail". Dog crates work great (and conveniently fold up for storage when you don't need them), but anything with a wire bottom will do. I've built some and I have dog crates I use. For the dog crates, I cut a piece of HC to put on the bottom.
Make sure the jail is large enough for the hen to move around a bit, and for food and water. Some people may put a 2x4 in for a roost, but its not necessary. Set it up about 8+ inches off the ground, so that air can circulate underneath her. I like to keep my jails in the main run/coop if possible. It makes reintegration easier and less dramatic.
Place your broody in jail and leave her there for a few days. Let her out to socialize and dust bathe every evening with her flock, and watch where she goes when she's done. If she makes a b-line for the nesting boxes - toss her straight back into the slammer.
Keep doing this every day until her normal behavior has returned, and she ignores her "nest". One good indicator is that once they are broken, the broody time bomb clucking will stop.
The best thing to remember through all of this is patience. I've had hens break in a few days and I've had hens take a few weeks to be broken. I currently have 2 in jail. I will attach a picture of one of them shortly so you can see the setup.
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