The good thing about Korea is that those mines are largely concentrated in a narrow strip of land. You can clear out some roads, keep the existing fences around the rest, and mostly avoid the Cambodia situation.
In case any passers by don't know about an extra factor that makes Cambodia even worse: lots of the country floods annually. This means that you can clear an area of landmines, but then when the floods come it can wash in landmines from other areas into the areas you thought were clear. It's very sad :-(