Hang a batten board to prevent tile slippage.
Tiling out of plumb walls.
So you ve got that bottom row of tile.
Measure the wall where you will place the tiles.
A batten board helps you start your bottom most course or row of tiles.
Check your floor for level and walls.
How to deal with out of plumb walls for tile.
Install the wall tile in a pyramid shape.
I hesitate to bring this point up but i think guess your walls are out of plumb because you capped the metal upturn flange of the tub with the cement board.
Find the midline of the wall from ceiling to floor and mark it with a chalk line.
Tips for tiling a wall 1.
If this is not the case then forget i brought it up.
You will lay out your first tile directly on this line and your.
How do we deal with that doing tile.
If this is the case you could remove the first course of tile and cut the board above the flange punch the board in and screw it.