The dog crate sounds like a good idea, but I found out that a standard size chick can fit through chicken wire! The could squeeze through til about day 3 or 4. If you have bantams it would be much longer. I was like you, scrambling as I found stuff out with my first broody. Now I've built a broody pen. I've only had 2 broodies but both accepted the new nest with her eggs. I used plastic hardware cloth for the bottom 18". You can barely see it but I had to put some window screen around the roost, as the little boogers were up there while they could still fit through the chain-link holes!