Bogertophis brought up a good idea by using a base. When I was big into aquariums, some decorative wood was sold with slate bases attached to help it stand up in the tank. I did that once in an enclosure with a really cool piece of wood I had. It was a chunk off a tree's root system, so it provided sort of a half log, with a large, solid piece of root extending off one side. My BP who loves climbing would venture out on the root and would cause the whole thing to pivot downward. I solved this with a thoroughly scrubbed piece of slate. I just siliconed the slate to the wood and it became extremely stable, and then the slate is buried in the substrate. You never see it.
Used this method on my girlfriend's pesky guinea pig's food bowl she kept tipping over too