Our nest boxes in the arks are about 18" x 12" - one for every 4 hens. We also have a free standing nest box from a book called Smallholders DIY, which they like.
Perches 2" x 2" with the corners taken off - don't put them too high 12-18" off the floor or they'll damage their feet jumping down. Use good close grained wood, in good condition, so that red mite won't be able to live in it.