A beautifully crafted and long-lasting stall shower can take a significant amount of time to plan, bid, and fabricate, but it can be ruined quickly if the tile installer doesn’t watch other trades working in the same space.
Without some degree of surface preparation, it’s highly unlikely that a concrete slab or wood-framed subfloor will be flat enough to meet the requirements for large-format tile. A quick check with a straightedge often shows that a small area or perhaps the entire surface dips and undulates outside of industry standards.