Step-by-Step

Flagstone patio surfaces look best if they don't have sharp edges. One way to create graceful curves is with a water hose. "Charge" the hose by closing the nozzle and turning on the water. This makes the hose less flexible so you can form it into curves easily. Lay out the hose in the shape you choose and pour flour or sand all along its length. Or, use field marking spray paint to outline the hose location. When you remove the hose, you'll have a clear line marking the excavation area.

tamp

Dig up the sod. Remove all significant organic material, including tree roots 1/2 inch thick or larger. If you don't, the patio will settle unevenly as the roots rot. If this means you have to dig deeper than the thickness of the stones, fill in low spots with sand or soil.

Rake the area level and tamp the soil firmly with a hand tamper or use a power vibrating tamper for larger areas. Fill in and retamp low spots. Install edging, if desired, before you lay the stones.

pattern

Start with large stones around the perimeter. If a stone is too high, pick it up and dig out some soil; if it's too low, add some soil or sand beneath it. Test each stone to make sure it does not rock. Work slowly and take breaks; this kind of labor can harm your back even if you do not feel a strain.

cut stones

Wherever possible, use uncut stones. When you have to cut a stone, lay one stone over the one it will adjoin and trace its outline with chalk, a pencil, or a scratching tool.

Use a brick set and baby sledgehammer to score the line, making a groove about 1/8 inch deep. Set the stone on top of a scrap piece of wood. For large stones, have someone stand on the other end. Split the stone with a single blow from the sledge. If the scrap piece is large enough to use elsewhere, protect it with a lumber scrap. You may have to make more than one split if you need to make a curved edge on a stone.

joints

Shovel dirt into the gaps between the stones, taking care not to get too much on the stones. Wet the patio surface with a fine spray, cleaning the stones while thoroughly wetting the soil. Fill in low spots, spray again, and repeat until you have level-looking joints that are about 1/8 inch below the surface of the stones. Plant the gaps with grass seed, moss, or a low-growing groundcover to discourage weeds from growing.