Lay paving stones in sand when you think you might want to change the arrangement later or when you just don't want to bother with concrete or gravel. This method is best for random patterns with space between the stones.
Clear the area where you intend to lay the stones.
Build a retaining border to keep the sand in place. It can be made of weather-treated wood, brick, or plastic edging.
Dig out the soil a little deeper than the thickness of your stones.
Lay a shallow layer (about an inch) of sand. Spread it with a rake.
Arrange the stones in a suitable pattern, keeping the smaller ones toward the center and the larger ones at the perimeter.
Tap each stone with a mallet (buffered with a block of wood). You want to make sure each stone is set evenly and isn't going to wobble.
Use a 2-by-4 board and a carpenter's level as you go, making sure the stones are level.
Press smaller stones into areas with large gaps.
Pour dry sand in piles along the drive or walkway and sweep the sand between the stones with a broom.
Water the area thoroughly, let it dry, and then fill in the low areas with more sand.
Because of their shape, you may need to build up the spaces below some of the stones with sand as you're setting them. Don't use other stones, however, as they will eventually break off and the stone above will sink. You may want to rent a plate vibrator. Go over the entire area to press the stones into place and insure that they're level.