I love microwave bowls but I hate how long it takes to mark them. When I made the last round I think that was the most tedious part. Google any tutorial for them and you will see the process.
Here is how I do it now. I cut the fabric and batting per the instructions. I fold the batting in half and mark one inch from the center then 2" down from the edge on the fold. I fold the batting in half in the other direction and repeat.
Can you see the marks at the top, bottom and side?
Here is what it looks like when open.
I lay the batting on the fabric square and fold the whole thing in half and sew my darts in each end. I refold it and sew the darts in those ends and continue on with the directions as normal.
Let me know if you have questions.