Depending on what you want to create exactly, it is possible to create such things from existing cliff or rock models. As you mention Saught, one of his mods contain some awesome rock pieces that can be recolored with textures from the web. Those are fantastic to create rock faces or cliffs.
Hills are abundant on several maps in all kinds of shapes, I usually pilfer from them and use them myself (you are free to pilfer anything from my maps too). The great thing about the hills is that they can be stretched and pulled into all kinds of shapes with Gizmo. You can make a large and flat hill or a small and high hill from the same model! A bunch of these hills together can be used to construct a valley, with the help of a few rocks to cover the seams.

Though for really complex shapes that really have to be a certain way, a custom model is still the best option as it just gives the most control.

ty king