I got the original idea from
PinCutSew on YouTube but I would say if you already make hot pads, follow your favorite method but make it big enough to plop a 9x13 casserole onto, and lose the hanging loop if you use them because that would be silly to hang. To make it easier on myself last year I did opt to sew mine up inside out, flip and topstitch around the edge instead of bind them. It saved a ton of time on a kind of utilitarian item that will last at most a couple years use.