I use my a laundry basket inside my clawfoot bath tub in the spare bathroom. Many use dog crates, both plastic and wire. I built a couple of simple boxes out of 2x4 and covered with hardware cloth and attached a door. These double as broody boxes for a hen with new chicks for the first 3 days.
I use a dog kennel that's 30" wide X 48" long by 33" high. It folds up really well when not in use and I store it in my spare bedroom, which is also the chicken hospital. I LOVE this kennel so much I bought a second one to just keep as a hen hospital kennel, since my original one is actually for puppies (which I am getting a new one in January). I put pine shavings in the bottom and I have a roost pole I add once a sick or injured bird looks well enough to try roosting. I also bought two slide in crocks from tractor supply-they have a backing plate that screws them onto the kennel and are GREAT for food and water without spilling. You can place them at any height you need and they have a clip that slides over the edge of the bowl to keep it from being knocked out of its holder. This also doubles as my broody buster when necessary-just place it in the run up on blocks.