The Laying Surface Must Be Even. The smoother, the Better the Clutch of the Tiles. On the Other Hand, A too Flat Surface Does Not Provide the Desireed Degree of Adhesion, and the Solution Or Glue Will Not to Fix The Fix The Fix The Fix The Fix The Fix The Fix The Fix The Fix The. Before Applying Glue and Laying Tiles, Plywood Is Necessarily Grinded.