That's already better. But something bad happened. The tiles, which are stuck together on a mesh backer, started separating from the mesh! I think the mesh is made out of some kind of water soluble material, and as we scrubbed, tiles were popping off and rolling around. What a nightmare! We used flat cardboard to transport them to some plywood in the garage where we could determine what to do next.
To keep the mesh from drying and sticking to the plywood, we coated it with layers of wax paper. We then used tile spacers to re-space the tiles on the mats properly. Not all of them fell off, but a good many did.
The thing is, you HAVE to wash the tiles in order to seal them, so I don't know how other people do it. Luckily for us, the tiles were dried back onto the mats a few hours later... For the most part. We applied sealer next. The sealer we used was a color-enhancing sealer, which darkens slate and gives it a sort of glossy look. It's not a high gloss, "wet" effect, but it makes it nice and polished. Our research had shown that alcohol-based penetrating sealers were the best for natural stone, and to absolutely not use anything water-based. Our sealer was the only Penetrating/Color-Enhancing Alcohol-based sealer in the store. Perfect.
The left side shows the tile with sealer on it, and the right is without. You can see some bubbles in the sealer on this picture, because I had just applied it with a sponge. I found dabbing and blotting the sealer onto the tile was the most effective way to get it down into the slate, especially on pieces with deep ridges or pits in them. Within five minutes, you use a lint-free cloth (we used painter's rags) to remove the excess sealer.
The next morning, the sealer was totally dry and we went to Home Depot to rent a tile saw. The saw uses water to cool and lubricate the blade, so we were again concerned about those mesh backing mats, and if they'd hold up to the saw. The short answer is sort of- many tiles fell off again.
We applied white thinset mortar to the walls, using a 1/4" trowel to remove the excess. The mats were pressed into the wall, and any missing tiles were placed in by hand and we used tile separators to get the spacing right.
One thing to note about this tile is that the beehives weren't a perfectly consistent size, making the spaces uneven in some places. They're also not consistent in thickness, so in this photo, some gaps look HUGE because the shallow tiles show more mortar. We had to use a lot more thinset than expected, too. I think this is because the thicker tiles were pretty hefty, possibly. Grouting will be a challenge.
We made sure to maintain 1/8 - 1/4" spacing between the lower tiles and the countertop, protecting the counter from the mortar with painter's tape. We were able to cut the tiles for the edges and outlets by making full scale templates of our wall and openings, and laying tiles on top of it or underneath it to get the right cuts.
The tiles were kind of disappointing to work with. Aside from separating from the mats and being non-uniform, the mats weren't 12x12 as stated. They're 12" tall and about 10 1/2" wide, so we were glad we bought more than enough extras. The biggest problem was that some of the slate tile faces sheared off of the tiles. The sealed faces broke off parallel to the backsplash wall, so we had to cut out those tiles and replace them with others before the thinset cured. Slate isn't super robust, and since it's made up of layers, it's understandable that some layers might peel away, but I think Daltile should test those tiles, or find a way to identify the unstable ones. Luckily, we caught it early on and were able to look at
Eight hours later, we had a backsplash:
Now we just need to grout and apply more sealer, add some trim, and we can call this one done!

