How to cut a hole into a landscape?

I checked at the Content Examples Landscape map and I managed to cut a hole into that landscape without problem.

But when I wanted to do the same with my material the landscape (part of it) become black. I am testing stuff in the ThirdPersonShooter example.

I even migrated the Content Examples material to my project but without any luck. It gives the same blackiness.

I also checked this:

but there is no simple material setup with the LerpHeight Node. I have 3 textures only. Maybe I’ll use 4 but not that many that the link has.

Well the workaround for a similar looking landscape is here:

You cam play around with the parameters to get more close to a LayerBlend node.