There are lots & lots of easy low-cost or no-cost things you can use for nesting boxes. Maybe we should have a section in the coops forum just for them. Hens will make their own nests by themselves, the only reason for providing nest boxes is to make the job of collecting easier for us humans.
They just like something rather cozy & secluded. Have some soft dry bedding on the bottom. Place it where it will stay dry & not too hot. Have it handy for you, so collecting eggs won't be such a chore.
Look around your place for things you could use, buckets or boxes or bins or drawers. You shouldn't have to spend much, if at all, to furnish nest boxes for your hens. Put golf balls or fake eggs in them, to inspire your hens to lay there.
I didn't get my nest boxes completed in time before mine started to lay and they were laying their eggs on a storage shelf I had in the coop. So I just put a plastic bin on the shelf and they laid their eggs in that. It was a great temp nest.
When I got my nest boxes completed, I put the plastic bin in one of the nest boxes and removed the storage shelf. The next day my BR laid an egg in the bin in the nest box. I removed the bin and now she and the others lay in the nest box.
I would just get some inexpensive plastic bin with maybe 4 inch sides and put them on a shelf in your coop. Just make sure they are secure so they can knock them off the shelf.
When the hens lay in the hen house they are using a wooden winebox/crate that has some hay in side. The community "box" outside the coop are my two dog crates I used to bring new hens home in. They are about 10 feet from the hen house door in the barn aisle way. There is hay inside and they have rounded out a nest and will lay in there when they lay. My current problem is nobody wants to lay other than one of my Dominiques once a week