Last month we had a Buff Orpington hen go broody, and (despite the worsening weather) to allow her to try hatching a dozen eggs. Her nest was in an area of the barn that a lot of other chickens had access to. Unfortunately, over the course of the next week or so, a number of those other hens got into her nest and laid some eggs of their own. When I checked back on it, she had 17 in total. That's a lot of eggs to keep warm, and those laid after the initial dozen would have different hatch dates. Plus, looking ahead, assuming she did manage to hatch some chicks, I wanted her to have a more secure place to tend and feed those chicks.
The best solution was to move one of our 4' x 8' chicken pasture pens in from the garden, and put it on a tarp in the upstairs portion of the barn. There are no animals (other than barn cats, as Homeschooled Farm Girl just pointed out to me) upstairs; it is just a hayloft and basketball court. I then covered the tarp with a good layer of straw, and set up a 5 gallon waterer. I also filled a feeder with grain, and then Henny Penny's new condo was all set. (This, incidentially, is the same way we brooded the large numbers of baby birds we got from the hatchery in the spring --- but with a heat lamp instead of a mother hen.)
I went back downstairs, and then carefully nabbed the (indignantly clucking) Henny Penny and put her eggs into a box with styrofoam peanuts. With the hen under one arm, and the box under the other, I made my way upstairs. Once the eggs were arranged into a new nest, I set her down next to it. After another several indignant and scolding clucks, Henny Penny carefully climbed onto the eggs and made herself comfortable.
Finally, I put a lid on the pen to keep her in and any troublemaking barn cats out. With all that feed and water, I knew she wouldn't need any further attention from me for quite some time.
Sure enough, a couple of weeks later, the chicks have begun hatching. There appear to be three little peepers so far, but she's keeping them very much under her fluffed-out feathers ao it's hard to tell for sure.