Excavate a spot to place your patio. Use a spade to dig down into the soil and remove a total depth of 10 inches of soil from the area. Remove the soil from your work space using a wheelbarrow. Check the depth with a tape measure and then check the area with a level. Remove additional soil to create a slight downward slope away from the house to prevent rainwater from pooling against the home's foundation.
Tamp the soil down in the patio area using a hand tamper. Pound the tamper down against the ground to compact the soil. Check the levelness of the area again to ensure the ground slopes away from the house.
Apply a 3-inch layer of coarse gravel to the bottom of the patio site to promote proper drainage in the area. Tamp down this layer of gravel and check the slope of the area. Apply another 3-inch layer of the same size gravel. Tamp down and check the slope of the area again.
Apply a final 3-inch layer of crushed stone on top of the coarse gravel. Tamp down this material and check the slope again. Adjust the layer as necessary to maintain the slope.
Begin applying the flagstones to the patio surface, starting against the house and working outward in all directions. Leave a half-inch gap between the house and the flagstones and between each flagstone. Use a rubber mallet to tap the flagstones into place, maintaining the downward slope away from the house. Continue to place flagstones until you fill the entire patio site.
Dump a wheelbarrow full of masonry sand onto the patio surface. Use a broom to sweep the sand into the gaps.
Compact the sand into the gaps using a masonry trowel. Apply more sand as necessary to fill the gaps between the flagstones after the compacting the sand in the gaps. Sweep extra sand off the patio surface.