Welcome to BYC. I just started with chickens over the summer and the people of BYC have been very very helpful. Feel free to drop by my BYC page which has my informative or amusing blog links.
I have seen pics by others here that used clear plastic storage tubs with hardware cloth over the top. One member, who has a regular system for doing this, even cut half the top out for hardware cloth so the other half would help retain heat better.
The usual rules of brooding apply. Make sure the chicks can get close enough to the heat to be warm and far enough away for comfort. They will need room for food, water, and walking around. Make sure the sides are high enough and the floor space is big enough for the final size they will attain before you evict them.