I position the larger rocks first... using the base rocks to fill in the bottom space, but the upper rocks have and inch or two of space behind them. Then I fill in with gravel to blend it all and give it that 'downhill appearance'. The gravel fill also adds to the stability of the rocks.
That space behind the upper rocks will be used for planting and adding decor.
And then you can pile gravel on the larger surfaces to add plants there also.
Another trick is to yank the bases off fake plants and tuck them under the edge of heavier rock.
I also use bigger rock chunks from breaking up the rock to take up space under the gravel in deeper parts.
Thanks for the compliments!!