First cut your coordinating fabric in 10" squares, cut your batting in 9" squares. If you plan on using in the microwave use 100% cotton fabric and batting as well as thread. Any polyester will spark and cause a fire.
Center your batting on the wrong side of each fabric square and sew from corner to corner as shown. I used a slightly longer stitch and thread that matched the fabric.
Fold the fabric in half and mark your darts. These darts are 1" in from the fold and 2" down from the unfinished edge of the fabric. Repeat, folding in half the other way. This will give you four darts. Sew darts and trim to 1/4".
This is what you should have after the darts are sewn.
Pin the two halves together matching darts, and points. Leave about 3" open to turn the cozy right side out (found if I left a bit more it was easier to turn). This opening should be centered over one of the darts. Clip the curves, the pattern I followed said to trim to 1/4" but I didn't do that and it seemed to work out okay.
Turn right side out. Pin opening closed and top stitch around the cozy.
There are lots of how to videos, and patterns on the internet. I found these a quick sew once I settled down and got them done.
This fits a soup bowl nicely. I have heard that you can make them larger for other sized bowls and I may sometime in the future give that a try. I am sure I can find pattern ideas for bigger ones on line. It is a great way to use up those bits and bobs in a persons fabric stash.
Everybody have a wonderful evening.