Changes

Paving underground(in mines) can be done by first reinforcing the mine floor. To reinforce, activate a [[support beam]], right click the floor tile, and choose reinforce'''Reinforce'''. After the tile is supportedreinforced, apply 1 mortar to the reinforcement by activating itthe mortar, right click clicking the tile, choose prepareand choosing '''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.