For the bottom or top? Top totally, bottom fuck right off with your hospital corners.

Fitted

I used to be on team no flat sheet. But then I got annoyed at changing the cover on my king size quilt and annoyed at fitted sheets that were cut too small to actually fit the mattress, and I am currently on team 'three flat sheets and a doona' and I use a flat sheet on the mattress and on top & bottom of the uncovered doona. It would be a perfect system if Mr Woof didn't insist on pulling everything apart and piling it into the middle of the bed, but there is nothing I have been able to find so far that is able to resist that.

Team flat sheet on top, and either fitted or flat underneath. I have an aircell blankie under the doona for winter, over the flat sheet on top. Comfy and flexible. The undersheet I really don't give a damn as both are functional, but flat sheets are MUCH easier to wash (and dry!) than fitted and in winter that does make a difference so flat sheet is easier to wrangle at this time of year. In summer when washing them is easy then fitted as the undersheet is preferable as cooler and less likely to get into a sweaty tangle.

Fitted + Flat. Doona for winter, wool blankets for summer.

Fitted and flat. Means you don't need to wrangle with changing the doona cover so frequently, and you have something to lightly cover you on hot days.

flat sheet on the bottom. I can't put on the fitted as my hands have too much arthritis now.

and a clean doona cover every week too.

I love a flat sheet. Unfortunately for me, somehow the man manages to wrap it around his legs during the night which annoys me, so no more flat sheet for me. 😔

I hate flat sheets anywhere on or in the bed. I overheat so easily under a doona already, I don't need another layer to add to my sleep discomfort.

And flat sheet on fitted sheet sucks too because I just end up tangled in it, leaving me all twisted and contorted by morning.

I prefer the flat sheet under the fitted sheet; makes the bed feel more comfy. Doona for winter, and a blanket for summer is enough for me lol