I grow on a horizontal trellis when I need to keep them low. I build the trellis from stout cord or wire cable stretched between trees, stakes, whatever's handy. I bend and kink as needed to distribute the branches over the trellis, and then clip the tips. Much like training vine berries, hops, or grapes. That makes all side branches grow upward. I keep pulling the dominant branches down, making them longer without getting taller. If they look like they'll outgrow the camoflage, I clip them back EARLY. Outdoors especially, pot has a period of very rapid growth as the days begin to shorten (or light is cut back). You want the plants to go into bud as fully recovered from any pruning as possible.

Outdoors, I've "unwound" horizontally-trained and twisted plants that were less than 5 feet tall (limiting factor was a 6' fence), but 11 feet long.

But often it's the smell, even outdoors, that attracts attention -- especially from folks who know what growing pot smells like. So just as important as keeping it low is keeping its odor covered with something. There's this plant growing across the street from me, near a lake, that makes me stop and perk up sometimes because it smells so close to pot. If I can find out the name of it I'll post it.