===Subterranean paving===
Paving underground(in mines) can be done by first reinforcing the mine floor. After the tile is supported, you can apply 5 mortar to the reinforcementby activating it, right click the tile, choose prepare. Once the tile is prepared, you're able to perform normal above-ground paving methods(all above options are available underground as well).
It should be noted that paving diagonally is not possible whilst underground.