The ground is not flat enough!

[Belcanzor]

Not completely sure about, but I think the terrain in my area is trolling me.
Every time I try to build the mine same msg: "The ground is not flat enough. Problem?" Well maybe I imagine the terrain say "problem".
This is the situation: I build my lean-to and claim close to the place where the mine future entrance is. Terrain must be flat, ok.
Well, I make all terrain same color and the final 2 tiles are too close to leanto/claim, and msg say I cannot dig because no clearance. (Problem?)

1 question: Flat mean that all the floor need to be red using the terraforming tool, same as the boston floor?
Or mean all the floor must be same color?
I can refill all the area and make the mine in a tiny mountain?
Finally: I begin moving the lean-to, rebuild the new one fast, and appear that I cannot destroy the old one (problem, weak noob).
Suggestions?

[Ass_Kraken]

I assume you're using ender's flattening tool. They just have to be the same color, not neccesarily red. Hold down ctrl when you left click, it will bring the tile to the lowest point of the tile.

[Belcanzor]

Thanks. Itry now.
Only thing that not sure about is the destruction of the lean-to if the dig problem persist.
Edit: Everything fine. Lean-to is broken, I have 9 yellow, look like as low soak.