I start my chicks out in plastic tubs with hardware clothe tops, using a brooder plate for heat. By week two the heat plate is off during the day and they are starting to adjust to staying warm without it. I brood in the house until they are well enough feathered and the weather is warmed up enough for them to go outside, so I needed a quick transition brooder for a few more weeks.
Start with a 30" pet playpen that can be used indoor and out. They are about $35.
Now you need a 6X6 tarp, zip ties, and 1/2" plastic hardware cloth.
Zip tie the hardware cloth to the pen. Otherwise the openings would be large enough for chicks to squeeze out. Spread out the tarp under the pen and you are set to go.
A couple of plastic rods or a piece of wood to hang the feeder (helps to keep shavings out), something to set the waterer up on, and a cheap stepstool to hide under and they are happy.
If they start to fly out, use clothes pins to secure plastic bird netting over the top. When brooding is over for the year use wire cutting pliers to remove the zip ties, fold everything up to store and save it for next year.