Before you can lay your patio stone, you'll want to make sure your base layers of gravel and sand are as flat as possible. To do this, you'll need to use a screed board, which can be a new or old 2-by-4-inch board at least half as long as your patio is wide. While you can build your patio yourself, generally for screeding you will want to have someone else help you to make the job easier.
Dig the area where you want to lay your patio based on your preplanned measurements 5 to 6 inches deep. If your patio stone is thicker than 1 or 2 inches, then be sure to dig deeper to accommodate for the extra depth.
Spread landscaping fabric along the bottom of the patio area, and fill the bottom with 2 inches of gravel over the fabric. Run the rake back and forth over the gravel to make it as even as possible.
Add sand over the gravel to cover it completely and form a 2-inch layer over the gravel. Spread the sand as flat as you can with the rake.
Have a friend hold one end of the screed board while you hold the other and move to one corner. Hold the board firmly as you each move the board forward over the patio area, dragging it along the sand to level it.
Run the screed board over the entire surface of the sand until the upper layer is as flat and level as possible. If you need to work with one of you on top of the patio area, be sure to move around on your knees and only on the unleveled areas.
Start on one end of the patio area and begin laying your patio stone one piece at a time, working your way across the patio until all the stone is laid. Work on your knees when needed in the sand, but re-screed the area before you set stone over it.
Add an inch of sand over the stone once it is laid, and sweep the sand in between the stones to help anchor them. Lightly wet down the stones to allow the sand to settle evenly.
Continue to add sand over the stones and sweep, followed by wetting it down anytime you notice the stones being wobbly or rocking. If your patio is on the small side, try using a screed board that is as long as the patio is wide, making a simple pass or two over the sand quick and easy.