DaveFish reminded me of a trick you could use also which is nice for plants with roots. If you want more substrate and less rock burried you can take a clean fishnet stocking or plastic/poly net and fill it with your substrate or sand and place that as a "rock" to raise your actual rocks. Won't scratch your tank and is a nice filler.
I do like the branch btw. Didn't mention that earlier.
That is is good idea, basically a sand bag. Nice tip.