First you need your bowl, a scrap of cotton fabric just a little bigger than the lip of the bowl, a piece of rip stop nylon(i use food grade) or PUL(NOTE: PUL is actually not tested for or recommended for use with food. I do use it for personal use, but any covers i sell are nylon) and a piece of FOE(fold over elastic).
Lay your bowl, upside down on the nylon with the cotton underneath that.
Trace a circle around the bowl, about 2" bigger in diameter (i have patterns for standard bowl sizes but you can totally just eye it, it doesnt have to be exact)
Cut out both pieces and straight stitch all the way around. Use a basting stitch this is just to hold them together while you add elastic.
No pictures of sewing the FOE on, sorry. I needed both hands. But stretch the FOE as you sew. Either a long straight stitch close to the edge or a wide zig zag stitch. I add a loop of ribbon to make removing the cover easier(and so i can hang them on a hook to dry). Stretch the elastic tight as you sew. finish the ends as you normally would FOE(sew two sides together, wrong sides together. fold under end, whatever. it will fray if you dont do something though) Place on bowl.
I machine wash mine. you can also hand wash and hang to dry. Let me know if you have any questions:)