You could take a piece of wood, like a yard stick and make a large compass.
Drill a hole at one end (centered left to right the size of a nail), then drill holes measuring from that hole at distances 1/2 the size pizza you want (also centered left to right). 6" 7" 8" 9" etc.
Find the center of your peel and tack the stick to the center using the first hole you drilled.
Then put a nail in one of the other holes and swing it around to score a circle..
You could use food coloring in the groove to make it more visible.
Would be even easier if you have a router and a circle jig.
