I use boxes as well I have 5 set up right now they range in size according to how old the chicks are. I get washer or refrigerator boxes and keep them around. I cut them down to the size I want. Using a washer or dryer box gives you the added height so they can't fly out so fast. I also cut and put visquine plastic down then put my bedding. This has worked for me. When they get to bad just toos and start a new box. I also have a homemade brooder that my son built out of an old large speaker box. It is only 18 inches deep so he put chicken wire around it to keep them in. Its nice and easy to clean but the boxes are just as handy.