omak -- I used a plastic gal ice cream lid around 8" in diameter. I think the site where I got my idea from used a 6" diameter circle. I wanted bigger squares in the middle so chose the bigger size plus that way I didn't have to make a 6" template. The squares on mine are a little shy of being 6". I hope this helps. I would suggest to make sure you cut on the line you draw around your template, save you from having to go back and trim them up later. Good luck!!
The smaller circles might be easier to work with but since mine was around 6' x 6' just worked better for me.