For just a few chicks, this quick and easy brooder works just fine. I nested an old cat litter box (well-cleaned!) into a snugly fitting cardboard box. The box I used is 13″ x 19″ x 11.5″ tall. The bottom is covered with pine shavings, the kind you can find at any pet store. The food and water dishes are just kitchen ramekins (heavy enough that the birds can’t knock them over by perching on the side).
The heat source is an incandescent gooseneck lamp. I start with a 60-watt bulb for the first six days or so, then reduce to a 40-watt for the next 5 days, and after that the chicks will do fine at room temperature (about 69°F in my kitchen), so I replace the bulb with an energy-efficient one that gives only light, no heat. And at that point, I can finally turn the light off at night. That’s great because it means the chicks will start sleeping when we do–much less noise in the wee hours!
I don’t clean out the bedding, just throw a handful or two of clean pine shavings on the floor of the brooder each day, or whenever it’s looking too poopy. Joel Salatin says in his book Pastured Poultry Profits that healthy bacteria actually build up in the bedding over time, lowering chick mortality. I do have to change the water every 3 or 4 hours, though, because the chicks are always scratching the bedding around, and a bunch of it inevitably lands in the water dish. You could probably avoid the perpetual water changing by buying a specially designed chick waterer at your local feed store.
Like I said, this set-up only works for a few chicks, up to 6 or so. Chicks grow very quickly and more than half a dozen would soon run out of space in a box this size.
Also note that it is imperative that your box have a lid. You may think of chickens as flightless birds, but they’re not! They don’t fly long distances, but they do like to fly up to roost on high objects. That’s how they protect themselves from predators. And young chicks are bent on exploring. So keep a lid on it! Note, too, that a lid helps keep down the dust. Chicks will eventually spread a thin layer of dust over everything nearby….
Hope this helps you get started on brooding your own chicks this spring! Let me know if you have any questions.
gettin' fresh! 
Oh, I hope to have chickens one day! This is a great example of using what you have, rather than just going out to buy something. I’m sure it is fun to see their progress! How long could chicks stay in this brooder?
As far as their size, they can stay in this set-up for 4 or 5 weeks. By the time they’re 3 1/2 weeks old, they have enough feathers to tough out freezing temperatures, so that’s when I start gradually acclimating them to the outdoors. In the first week of April or so (I’m in Zone 7, where average last frost is April 15), outdoor temperatures are warm enough and the chicks are hardy enough that I can move them to their own special corner of the chicken coop, where they’ll start getting to know the older chickens from behind the safety of a wall of chicken wire. And then, when they’ve reached full size several weeks after that, they go in with everyone else!
Thanks!