Lay the two pieces of rope down, following the exact path you want for the walkway. Place one end of the rope where the walkway will start and adjust the distance between the two pieces, to show the exact width of the stones. Arrange the stones in the center and remove the ropes. Walk along the stones, adjusting each one as needed until it feels comfortable walking on the stones.
Place the edge of the garden spade at the bottom corner of the first stone. Slide the spade along the ground, leaving a mark in the ground that shows the outline of the stone. Repeat the process on each side and on every one of the stones. Then, remove the stones from the ground.
Gently scrape the grass from the lawn inside each outline of the stone. The stones should sit directly on top of the dirt and sand and not on top of the grass, which can become slippery and cause the stones to move. Dig underneath the grass with the spade, removing any roots below.
Pour a small amount of builder's sand on top of the dirt and level it out with the spade. The stones should sit slightly higher than the surface of the ground, as the sand will break down over time and cause the stones to sit even with the ground.
Place the natural stones on top of the sand and try walking across the stones. If the stones feel uneven or move, add a small amount of sand or even out the existing sand. Once the natural stone walkway is in place, pour a small amount of mulch on each side of the stones to keep them from moving.