Thank ya'll. For batting, I used my regular quilt batting-cotton 80/20. The Youtube video that I watched had you cut 2 squares of fabric (8 1/2") and 2 squares of batting (1/2" smaller).
The first one was too small for my bowls, so, I increased size (on these) to 11 1/2" . Much Better. I used the salad plate to trace circle for spiral stitching.
I don't put them in the microwave.
I have made oversized flat "hot pads" using double batting. One stays on the counter next to microwave for hot items to land! It is a large spiral seashell. Will take a pic and post! Everyone I give one to loves them.
here's the link to the pictures I posted:
Nautilus Hot Pad