Drive the stake at the center point of the ring with the rubber mallet.
Tie the twine around the top of the stake, loose enough to rotate freely around the stake as you walk around it.
Tie the other end of the twine to the spray paint can. Choose a color that blends best with the stone, mulch, or soil as you choose.
Keep the twine taut as you walk in a circle around the stake, spraying your circle guide.
Remove the stake and twine. Remove the sod within the inner perimeter of the ring by stripping the grass with the shovel at roughly a 30-degree angle. This process is called strip-sodding, and is a preparatory step prior to planting or making fire beds.
Begin laying your stone along the paint circle. Make small adjustments to each stone as needed to perfect the perceived roundness of the enclosure.