If you've ever seen Fresh, then you'll be familiar with the chicken tractor. Joel Salatin uses them. Lots of folks have jumped on the wagon (pun intended). Kent build our birds a real nice tractor.
It's 8 feet by 4 feet excluding nest boxes, has a built in ramp/door, nice big tires, and can be moved around by one person.
The nest boxes are accessible by flipping up their roof and they are set on the outside of the floorplan, so they don't cramp the hens. Technically, the hens could do with just two boxes, but Kent was building deluxe-style, so there are three.
The whole thing is covered in chicken wire to protect them at night, and then covered with a tarp for shade and rain protection.
For the first week we confined them to a small portable yard when they weren't in the tractor. It was to get them used to their new locale. They can come and go from their house as they please throughout the day. Water and feed are inside so that they are less likely to get pilfered or infested by other creatures.
The ladies did a thorough inspection and they seem pleased with it. I know we are.
Each day we can park it in a new location so that they find fresh bugs, grubs and plants and they put less wear and tear on the land. Unlike my last flocks, which had a small stony yard that never changed, these birds have it good. We quit using the temporary fenced yard and now they free range when not in their house. At night, they find their way back to roost and we close it up securely for their protection. It's a great way to do chickens!