Stone flooring - Tile Advice

[PC Tile]

What's your tiling question? Pictures can be added.
Hi all,,,,large format ! Stone 900x900x20 onto old and rough concrete floor,about 700 s.m any advice,,experienced tiler,many years but not with these.Any help appreciated,,,many thanks PC

 

[Dave]

What's your tiling question? Pictures can be added.
Hi all,,,,large format ! Stone 900x900x20 onto old and rough concrete floor,about 700 s.m any advice,,experienced tiler,many years but not with these.Any help appreciated,,,many thanks PC

A good strong back 😂.

any cracks in the substrate and is it various rooms or one area. ?