Can we not say "nel letto" here? (Much as we say "nel piatto" and "sul piatto" interchangeably?)
when do you use "guanciale"?
Idiomatically it can be used to mean "to have no worries" or "to sleep easy" in the phrase "dormire fra due guanciali" Not too sure about its general use but suspect it is just another word for "pillow."
I pretty much never heard "guanciale" in my life so..... use cuscino if you want to say pillow ;)
it's the same thing