I just wanted a little blanket for my casserole to keep it warm and be able to handle it a little easier when hot. With some quilted double-sided material (of course, you could make your own) I cut out enough fabric to come up to the top of each side and a little extra on the ends to act as pot holders.
Then to get it to hug the dish, I sewed two darts on each corner,--
--using pins, just make darts as if fitting a dress to a mannequin. I basted mine first since there is no pattern to follow and pulled out a couple to restitch.
After trimming around the top to make it all symmetrical, I made some bias tape trim and applied to the edges for the finished look.
I just turned the darts towards each other on each end and made that my inside.
Then when serving, tuck the ends down to keep food from getting on them. This particular dish has "handles" which it works well on.
A straight sided dish would not need the longer ends.