Take a cardboard box (I used a printer paper box), take the top off and stand the box on end. The end should now be the top. Cut a hole in the new top almost as big as the box but small enough to set a brooder light (with the metal cone) on without the light falling through. Cover the hole...
I just get lucky sometimes. I take a couple hundred pictures and get one or two worth sharing. Someone posted on BYC how to make a light box. I don't remember where I saw it, but it's easy, cheap, and makes great pictures. Especially when the chicks is photogenic and cooperating.