Hi,
First, begin with the end result in mind. What do you want the tank to look like in the end? Aquascaping with rocks exclusively is known as
iwagumi. If that's what you are after, then use 3, 5, 7 or 9 rocks for the basis of it.
Second, divide the aquarium into thirds and place the main, large stone at the third line, either right or left. Then begin placing stones, one at a time, in such a way that their position naturally supports the big one. Try to build up stones around the third line that you used for the big one.
Third, place some of the final smaller stones on the opposing third (on the other side) to balance the layout. The stones should typically be pointing towards the larger rock and the larger rock should not point up and down but at an angle.
Lastly, triangles are your friend. Here's an analysis I did go
George Farmer's One-Pot Iwagumi. It will give you some idea of how George built his rock aquascape.
Good luck and let us know how it goes.