Our Barred Rock and Rhode Island Red Hens have a cluster of sixteen metal nesting boxes attached to the rear wall of their chicken coop... all lined with straw.
Our hens are a flock of six. They could each have their own nest. However, five take turns laying their daily egg in one box and the sixth on top of a bale of hay where she has hollowed out a bowl-shaped nest.
Then, one hen... and later two... started hanging out in an old wooden nesting box that we had, several years ago, attached to the wall of our front porch just for quirkiness. If we had extended an invitation by lining the two units with straw, it wouldn't have struck us as odd, but the hens identified it as a nesting box on their own.