Installing stacked slate tile
Apply the Thinset
Installing the slate follows the same procedure as for any other tile: Apply thinset to the wall with a 1/4"x1/4" square-notched trowel (Image 1), place the tile and wiggle it into place for maximum adhesion (Image 2). This design doesn't use any grout; set the tiles flush with each other on the wall.
Note: If taking a break during tiling -- whether for lunch or to cut some custom tile shapes -- make sure to scrape any excess thinset off the walls so it doesn't dry on the wall.