When I mark my batting, I mark my batting and draw the + then center with a masking tape roll. After marking 1" on each side of + lines I just draw a V down to the circle on all sides. These will be your darts. Remember I make mine 12"square.
Most times I heat the bowl of food and slide out of microwave into the holder instead of cooking in it.
We are using for ice cream this summer to keep hot hands from melting it. Good luck all and make plenty.