First use a batting that is pretty stiff if you can.(100% cotton) I use a thin batting that is soft for my quilts and that doesn’t work very well. I suppose you could double it but I had some on hand that fit the bill. I’m sorry I can’t tell you what kind. The label only says 100% cotton and I’ve had it awhile.
Cut the batting an inch smaller than the fabric. I used a ten inch square and 9” batting. Sew just on the edge of the batting so there is no bulk at the seams. Clip corners.
Clip your darts. Speaking of darts, if you like a deep soup mug instead of a bowl make your darts a generous 2” long to make the cozy deeper.
Give yourself a good 4” to turn. Be sure to push out the corners with a chopstick or something like it once you turn it inside out.
Wonder clips work great for holding the opening closed.
If you are giving as a gift, make a card to go with it that tells the recipient how to use it and that it’s washable.
If you don’t have one of these you should make one for yourself. They really are handy. If you have made them and know what kind of batting you’ve found to be the best, please comment and let us know.