Originally posted by Grid_Nine:

Holding shift while leveling with the hoe on slopes may help.

As for the paving, I've noticed mine gets a bit distorted as well in some places. Like the ground is swelling in the middle and tapering off to the sides. In other places it is perfectly flat. I started to pave a long road I had going through a black forest and after a while I was like, dirt road it is.

Where does it tell you that you can hold shift to change the height like that?

That's awesome, thanks for letting me know.