I'm trying to terraform a section of the overworld, and need a flat grassy plain, yet can't find it in the creation kit. I notice most of the terrain can not be clicked on to pretty much lay down a flat grass floor, where can i get such a thing?

The exterior is not a Mesh Piece. Its terrain.

You can edit exterior terrain using the heightmap editor. Press 'H'. And make sure to look at the tutorials.

Yeah I was just reading about that, I assume they are still broken?

What's still broken?

If you're referring to the Heightmap editor, yes, it is still broken. It is just as buggy as it was in Oblivion, if not worse.

But the Landscape editor works better than ever, which is what he meant.

Ok, along this line of questioning: Grass, is it tied to the heightmap/landscape editor, or is there an easy way to remove it? I've got some poking up through the floorboards of my porch.

It's generated randomly based on the texture you apply to the ground. Use a texture that you know has none (Like a Dirt one) or a variant that ends in 'NoGrass'.

Awesome, thanks!