I just pile up the rocks such there there are lots of caves and swim throughs. You can go nuts with PVC frames (spray painted black), resin to hold rocks together, etc.
On one system, I went with a rock wall that looks good in a tall tank. In the other I went with a rubble bottom that has a maze of rocks, structures across the bottom, but there is little height. My clowns settled in and dug out a cave on their own.
It really depends on what sort of look you're going for and then how stable that would be without some sort of support system.
Be sure to put your rocks directly on the glass bottom and not the sand. There are lots of fish, shrimp, etc that will burrow under your rocks and destabllize them. Either use base rock or egg crate for the bottom.