we don't layer in our hutches/sheds or wendy houses.
We use lino to keep the hutch clean, then newspaper. Then, we use litter trays with newspaper, litter (NOT SHAVINGS OR SAWDUST - PROVEN TO BE UNSAFE FOR SMALL ANIMALS) e.g. Megazorb or similar, then hay on top. If you give them a big litter tray, and lots of hay, it'll encourage good hay eating, weeing and pooing in the tray, plus in this weather, it'll help to keep your bunnies warm.