Solved Admin build under map

As the title says, how do you build under the map as an admin? I'd like to make an Arena/Shop under the map so it's not in the way of players. I've seen it done before on RustyGaming. All help appreciated. Thank you.

 

Copy paste plugin with a negative height adjustment should work I assume?

 

You basically just build the shop/arena on the map and then copy paste it under the map.
There is a building plugin aswell that allows you to build under the map, but it takes time if it's a big building.

 

Thank you, appreciate it.