This is the tutorial I used.
I have quite a few of them and just love them.
I have put 60/40 wadding in them but this time I used all cotton wadding. The fabric is all cotton too.
These are only used for warming food for a very short time in the microwave. I would not recommend heating them for a long time. 2-3 minutes is plenty. If your food needs longer do the first few minutes without the holder and then put the bowl in the holder for the last minute or two.
They can also be used for ice cream too so your hands don't get cold. That's for the people who don't eat at the table..