You know the problem - you lay out a large pasture, and when it auto-flattens you realize that you inadvertently bit into the side of a hill (sometimes hard to see due to the Banished perspective)... so you are left with that squarish cut-out that looks quite unnatural... what to do?
Flatten Terrain Tool to the rescue -

Small Repair After Auto-flattening
You can see clearly where my pasture bit into the mountain... so I carefully cut in two or three tiles more, sort of a semi-circle... still looked a bit weird, but better. Then I thought - hey, a tunnel entrance would look cool here... and it does - even better than default, as it does not protrude as much as they normally do... enter
Moria!
