Hey I have bucket nesting boxes too!!
Picked them up free at the dump. I screwed half moon pieces of 2x6 in as "bedding holders" with one screw coming through the bottom. They swivel open for easy cleaning.
The nests are just sitting in the 2x6' peices that the half moons were cut out of - not attached.
Everything is easy to pull apart and remove from the coop for sanitizing.