Things to climb on and things to huddle under. They like to be higher than each other to flap their wings and feel superior. Maybe a swing. A sturdy branch for climbing on. Maybe a kiddie swimming pool with sand and wood ash for a dust bath? DE not necessary. It looks really nice!
If you have an extra window planter, or any flat planter box, you can cover the top with rabbit fence, or other wire fencing where the holes are too small for the hens to get their heads through. Plant chicken safe grasses and herbs in it with a gap between the dirt and fence to make a self replenishing grazing box. The plants grow through the fencing so the hens can’t devour it in one sitting. It makes for endless stimulation and will become a regular pit stop throughout their busy day