I just make a triangle out of three trees. Tie them end to end, and then tie a brick to a rope lanyard about 1-2' longer than the depth I'm putting the trees in. Kind of like an anchor until the clump sinks.

Excerpt from Robert Crais' "The Monkey's Raincoat:"
"She took another microscopic bite of her sandwich, then pushed it away. Maybe she absorbed nutrients from her surroundings."