I brooder still in cardboard boxes with litter in the bottem, set on top of a trash bag. I just use the boxes in the compost every 3 days when I change them for clean boxes.
Remember, you can read up on caging options in various threads, such as Coop vs Chicken Tracter...
When I got started, I bought the chicks and built a little chicken tracter for 4 hens and rooster while they broodered. I did not start in a coop, and didn't own a coop at all until 12 years into it. I picked up a 2 x 3 x 3 wooden shipping box on the road, put one board for a perch in it, put...