Walls | Do you need all tiles leveled?

Greetings,
Wondering how walls work in regards to tile elevations, do you need to level everything flat in order to setup a wall system?
Or is it the start area needs to be leveled and after that it doesnt really matter ..
Thanks!
Wondering how walls work in regards to tile elevations, do you need to level everything flat in order to setup a wall system?
Or is it the start area needs to be leveled and after that it doesnt really matter ..
Thanks!