In the picture above you can see the rocks in place for a Saikei with a foundation of clay, sand, organic matter (OM) mix.
I was asked on Saturday where the best place to get rocks for Saikei is, well in my experience the best places to try are aquarium places as they tend to have rocks which have an interesting shape and often are varied in size.
In Saikei it is often best to try to get rocks of differing sizes so that you can position them to create different heights, thus avoiding a uniformed look. I will normally start with a main rock and then select other rocks with similar charecteristics to act as the 'supporting rocks'.
Remember that when you do Saikei you will vary the texture of the rocks to suit the style of Saikei you are creating, i.e. smooth rocks best suit lowland or lakeside Saikei, whereas rugged rocks will suit coastal or alpine compositions.