Been raising chickens for 30 years and the best nest box materials I have found by far are. 1. Nice layer of pine shaving's 2. Good layer of pine needle's 3. Dusting Diatomaceous earth Remember your hens will move a lot of needles to their liking so add more if needed. Some conifers and fir's (pines) have stiffer needles than other's try to find the most flexible ones you can. Make sure their dry and clean, no mold, Pines have a natural resin the repels most insects so it's perfect for nesting boxes, I've never had a problem with pest insect on my hens. And if a hen gets messy it's easy to take out the soiled needles.