It's crazy how different each area of the USA is with how tops are quoted. This topic gets brought up at least once a year here on this forum! It's hard to advise unless someone lives in your area.
Here in the Ohio Valley area, you can buy from a box store, a K+B dealer or a fabricator and sometimes with your builder or interior designer.
You can shop by visiting a few places and giving them a layout to quote. Make a sketch showing number of sink or cooktop cutouts, brand/color, edge profile, backsplashes yes/no and if any countertop supports needed. Old top removal, haul away and plumbing hookup usually is not included but is available if needed by SOME fabricators.
If you know your square footage amount, you can go that route too...but keep in mind the price is ballpark only until they can template. size of slab and number of seams all need to be discussed at the template.
By the way, Calacatta Laza is really pretty.
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