Nesting Boxes are like maternity wards for chickens. It’s where they go (or should go) to lay their eggs. In general you need one nesting box for every 3-5 hens.
The nesting boxes should be big enough for your chickens to stand in and 12x12x12 will work. The nesting boxes should also be somewhat dark, and, to make your life easier, accessible from outside the coop.
Here are 2 things that you don’t want to do:
1. Make the nesting boxes higher than the roosts – Your chickens naturally will find the highest spot they can to sleep. If the nesting boxes are higher than the roosts, then that’s where they will go. Most people do put the nesting boxes off the ground, about a foot-and-a-half to two feet up. (Remember, don’t make it so high that it’s hard for the chickens to get into.)
2. Make the nesting box roofs straight – Even though you are going to keep the boxes lower than the perches, you don’t want your chickens sitting or sleeping on top of them, pooping them all up. That’s why you’ll see a lot of nesting boxes with slanted roofs – to discourage the chickens from sitting there.
Oh, one last little tip. When your chickens approach egg-laying age, put a golf ball into their nesting boxes. It may help train them that that is where they are supposed to lay their eggs.