I line my nest boxes with a folded feed bag; bag get soiled pop out the soiled pop in the new. My feed bags are woven synthetic material and in below zero temperatures soiled issues just pop off with a slight tug and they stay cleaner longer.
EASY PEASY!
I have two of them they make excellent nest boxes just as is!
For standard size chickens and especially Muscovy ducks!
Mine were just on the floor thank you very much
With a plastic egg or golf ball inside they were in buisness in no time flat!
Mine have tops however.
I saw somewhere...