How To Cut A Big Circle

This is an update on a post from last June about this wonderful vintage belt mat. I received an email from someone who posted on Instructables on how to cut a large circle and he wrote this to me-

"i wanted to tell you how to make a nice circle so
you can cut your mat. this is what i wrote:

to get a perfect circle you will need:

1 nail or pin
1 pencil/pen/marker
1 piece of string.

Tie the string to the nail pin, pull the string
out the radius of the circle and tie it to the
pen/pencil. Stick the pin/nail in the middle of
your belt mat, pull the string tight & then draw
around in a circle keeping the string tight as you go"
Thanks Intoon!
Instuctables link