First you need to determine the area and the shape of the patio.
there are really two ways to do this, one is more difficult, but very sturdy. The other is inexpensive, but will shift around with the ground conditions.
1) Dig down about 6 to 8 inches. I am assuming that the stone is about 2 inches thick. Get some bender boards and set up around the dimensions of the patio. This will be your frame for concrete. you need a metal fabric in there for support and to keep it from cracking. They use rebar on roads, but for this I would find some old chain link fencing. Keep the chain link suspended about half way through the cement.
Pour about 4 inches of concrete and screed it out. Allow about two days for curing. Then lay your stone in the way you want it to look. when its all layed down and good, then pour unmixed mortar all over the patio. Then sweep this mortar in between all the stones. this will by your glue to keep the stones in place and together. Once the mortar is all in its place, then lightly sprinkle the entire patio with a fine spray. This will set up the mortar for a set. make sure you apply enough water to penetrate to the bottom. Wait until its dry then scrub off the unwanted mortar.
2) dig the hole, pour in sand, water sand, pour in more sand, water sand, place rocks in sand and then do the mortar thing again.