There is a pic of one version in this link. there is a lot of good info at ATTRA if you haven't used it..
http://attra.ncat.org/attra-pub/poultry_equipment.html
Community and Tunnel Nests
A community nest. The lid is normally kept closed except during egg collection.
Community nests work on the idea that the hens prefer to lay in darkness, but they don't eat in darkness. This eliminates egg eating. The traditional community nest is a box four feet wide and two feet deep, with a doorway that's not much more than six inches wide and eight inches tall (and maybe with a flap of cloth or plastic across it). This is good for fifty hens.
Another variant is the tunnel nest, which is eight feet long, two feet wide, and has a small entrance at each end. This is good for a hundred hens.
Community and tunnel nests need to be well-ventilated without letting in much light. This is usually done by leaving the back partly open or drilling large holes in it (on the assumption that the nest will be installed to almost but not quite touch a wall of the henhouse). Sometimes they're installed at floor level, in the spots where the hens insist on laying in spite of having perfectly good nest boxes elsewhere.
Community and tunnel nests can be constructed as free-standing outdoor structures if you put a good roof on them. They'll probably need to be staked down to prevent them from blowing over in high winds.