You can wrap the texture around a corner of a brush. In some cases this will work, in other cases it pays to just make the geo a terrain mesh and use Set in the Surface Inspector.
To wrap: alt+mousewheel click on the top (flat) surface (it will select the face), then alt+mousewheel click on the angled surface. This takes the guesswork out of trying to find the correct angle in Surface Inspector and saves a lot of time.
There's a similar function in Surface Inspector for terrain, called Forward Wrap. It will wrap the texture around 2 meshes as though they were merged.