Set the Tile
Lay full and cut tiles while watching for straight grout lines. In this case, the handmade saltillo tiles are uneven and spacers are unnecessary. However, to keep grout lines straight when using more uniform tiles, use spacers between each tile. Push the first tile into the combed mortar bed with a twisting motion. Using a protective scrap piece of lumber, tap the tile with a mallet to set it. For the first tile only, pull it back up to make sure the combed mortar is think enough to cover the entire bottom of the tile. Spread more mortar in a thicker layer if the bottom of the tile is not covered completely when pulled up. If the mortar coverage is sufficient spread mortar in small sections and set tiles. Allow mortar to set well before applying grout.