Large-format slabs reward careful substrate prep and punish shortcuts. Before a single slab goes down, the subfloor needs to be flat to within the tolerance the adhesive manufacturer specifies -- for most large-format work that means no more than 3mm of deviation across a 2m straightedge.
Use a full-spread, back-buttered adhesive application rather than dabs or perimeter beads. Trapped air pockets under a slab this size telegraph through as hollow spots and eventually cause cracking under point loads.
Lippage control matters more as tile size increases: use levelling clips rated for the slab thickness you're installing, and check every joint before the adhesive cures, not after. Finally, leave adequate movement joints -- large format doesn't forgive rigid, joint-free runs across long spans. Get these five details right and a slab installation will outlast the building around it.