Awhile back I had 4 chicks in a cardboard box in the house. I also have parrots, and had purchased a "Snuggle Hut" for the parrots, which they did not use. It's like a little fleece/fabric hut with a hole in it.
I put it in with the chicks, and they LOVED it! They would sleep inside it, practice dustbathing in it, just hang out in it and preen. They got really good at barreling in and out of it. They used it until they couldn't fit through the hole anymore, and then they slept around the bottom. It was the cutest thing ever.