Spread thinset mortar on the bottom center of the wall.
How to tile a wall that is not flat.
The way i would approach this would be to get your top row correct and level then work down to the floor.
Test a tile to make sure the mortar is mixed and spread correctly.
A contractor was giving me an estimate on a tile job and he showed me how my walls are not flat.
Pull the tile up and look at the pattern that is create on the back.
In your case make the top edge level and do your cuts at the bottom whether or not you use base or cove at the bottom.
For the average small wall tiles which are currently popular you will want to use a 1x4 square notch trowel.
He held up a straight edge against the surface and showed me where some of my walls back off away from being straight in some areas.
Then every subsequent row is a process of draping over the pyramid back and forth.
If you can remove it cut off the back piece and scribe it along the wall.
The best way is to arrange your wall tile in a pyramid shape.
Apply it to the tiled wall with a grout float making sure to get grout into all.
Spread the mortar with the flat edge of the trowel then groove the mortar with the toothed edge until it is uniform in depth.
You already have a backsplash that 4 piece of countertop up the wall.
That way your counter will now sit flush against the entire length.
Take a tile for the edge of the wall and apply the adhesive to the back as if you were putting butter on a piece of toast.
Mortar a small spot and then place a tile.
Install tiles one through four as directed.
So the tiles end up not being flat to each other but it doesn t seem possible to correct this as if i squash down on the one side the other side pops up.
If it seems complicated try this.
The other alternative is to run the wall tile doewn behind the floor tile with a 90 degree corner there.
Putting tile on top of that doesn t look good especially w a busy pattern countertop that you ve chosen.
Grout any tile job by mixing powdered grout and water to the consistency of peanut butter or use premixed grout.
Then position the tile where it needs to go and add the spacers.
Hang edge tiles by applying adhesive to the backs of the tiles.
I butter the back of each tile but scrape off any excess adhesive and put the tile on wall and twist it a few times holding opposite corners.