The substrate
What must the substrate look like?
Nothing works without the right substrate. It is the basis for the final work result. It doesn't matter whether it's about the appearance or the medium to long-term adhesion of the tiles.
The substrate must be clean, dry, dust-free, load-bearing and even. The larger the tiles, the fewer unevennesses the floor should have. Therefore, smooth out all unevenness with the spiked de-aerator roller or the surface trowel and use the cord irons as an aid for a straight line.