Make a Trench and Fill With Gravel
1. Mark your bed by laying a garden hose around the perimeter. Pour flour or sand on top of the hose, and remove the hose. You'll have a clear line.
2. Dig a trench 2 inches wider than the stones or concrete blocks and 3 inches deep.
3. Fill with 2 inches of gravel and tamp firm with a hand tamper. Add sand to come up almost to grade and smooth out to form a flat surface for the stones or blocks.
Stack the Stones
1. Set the first row of stones or blocks, butted against each other. Set the second and subsequent stones or blocks on top, staggering the joints for strength.
2. To cut a stone or block, make a 1/4-inch-deep groove in both sides using a brickset and a hammer. Lop off the waste side with the hammer.
3. Fill the bed with light topsoil that has plenty of peat moss or other organic material so it will drain easily. During heavy rains, water will seep out through the joints between the stones or blocks.