Apply just enough of the adhesive to attach a few tiles at a time so that the adhesive stays moist and ready to receive the tiles.
How to tile over uneven walls.
The floor slanting is not that much of a problem even for a do it your selfer.
The mortar is spread.
With a notched trowel apply the adhesive at the bottom of the cinder block wall.
As for the floor being out i would pick a comfortable height the lower the better and establish a level line and back lay the tile to the floor but i would not do that if you are really talking about true cove tile because you will end up with a cut edge on.
Mark the wall in the middle with a chalk line to create a guide for the tiles.
Don t use plaster or ordinary sand cement render or you will have to wait a minimum of 10 days before tiling longer the thicker it gets.
Hold the float at a 45 degree angle to the.
By uneven i think you mean that the walls are not flat.
Back buttering is a trick used for tiles of uneven thickness like ungauged slate or handmade tiles extremely large tiles or for tiles being installed on an uneven surface.
Comb walls then back butter tiles accordingly if they are really bad holes etc you can build out wall in layers using rapidset adhesive which will set in 3hrs which will then allow you to use your tub stuff after priming make sure you smoothe the rapidset otherwise you are giving yourself more hassle.