Note: Water does not flow in Wurm but I use it flow to explain slopes.
The best way to explain slopes in [[digging ]] is to think "Which way will water flow on that tile border?".
Wurms examining of the slope uses this idea to tell you how much higher or lower is one CORNER than the other.
And remember even if it does not look flat, If all 4 sides of a tile is flat - ITS FLAT.
==Visual guide==