bare-arse

With the buttocks exposed, as for a spanking or a mooning.

Stark naked.

So he's pounding them off and is away over the hill in sweet dreams, and Clarice tippy-toes into the bedroom as quiet as fog coming off a millpond, and she takes off her clothes and stands there bare-arse looking out the window in the moonlight.

"I sleep bare-arse, Mrs. Bayram, always have, which you can come and check out any time you like."