Originally posted by GeoForce:

Game restricts you to only 8 meters or so below ground level so I dig down to that depth totally encircling the deposit, then mine it all out. Leaves a nice hole where you're safe from trolls and can easily kill them as they stand on the edge throwing rocks at you.

I've considered building a base down in one to act as a waystation when on longer trips.

My thing is to make a base surrounded by deposits in the hole of a central one. Makes it so you don't really have to transport the copper anywhere.
https://steamcommunity.com/sharedfiles/filedetails/?id=2559869412
Bonus for finding that next to a good swamp.