Seams are not invisible, and the patterns will not line up perfectly. We do our best to match pattern. In natural stone this is very difficult, as every single slab is different. It is easier to match pattern in Quartz as it is man made patters that repeat. We use a machine that sticks to the countertop using a vacuum pump holding it level and tight while the glue dries. The quality of the seam being level and visible is based on the amount of warpage and thickness variation in the stone. Some brands are better than others. We have examples of seams in the showroom.