Currently only trees can be placed on the hills. The list of objects that can be placed on hills will be expanded, but often you won't be able to place them. You need a relatively flat surface to place an item, like in real life :).
In this video trees are not visible because they are big and obstruct you view of the landscape, which is the focus of the video.
Sethiel
Seth joined
I am the game designer, lead programmer and very occasionally graphics designer for Dwarves and Holes (aka. DwarvesH).