Hi Stereo, I took some snaps of one of our wee broody coops for you this morning:
There's not much to it really - just a simple frame made from 2x2 timber screwed together, then covered in 6mm plywood and painted. The hardest things to make were the pop-holes, which are a sandwich of two pieces of ply with some spacers in between so that the door (a synthetic roofing slate) can slide between them.
If there is a broody in residence, she can still come and go as she pleases, but I lock her in at night against predators. Once she has chicks, I block off the wee entrance to the run part to keep them all contained until they're ready to go out and about with Mum. She will usually return with them to sleep in the broody coop until they're fully feathered, at which point she'll take them into the main house of her own accord.
All in all, it's a nice low hassle system which works very well for us
.