1. Start with the basins
Mark each bowl, tap and waste position, and the space needed around them. For an undermount sink, send the model and its cut-out drawing. For a bowl carved into the stone, agree its shape, the fall to the drain and the waste fitting on the drawing.
2. Mark the visible edges
Show which fronts, sides, upstands and aprons will be seen. A thick-looking edge can be solid stone or a mitred build-up; the drawing should say which, so the price and the look match.
3. Settle the support
A floating vanity needs brackets or a frame fixed into a wall that can take it. A top on a cabinet needs the cabinet sizes, a level bearing surface and drawer clearances. Your builder confirms the fixing for the real weight.
4. Place the joints on purpose
Long tops and complex vanities may need joints. Slab size, transport, bowl construction, vein direction and access all decide where they fall. We show the joints on the drawing before cutting.
5. Say who supplies what
List stone tops, bowls, aprons, upstands, returns and cabinets separately. Name who supplies taps, wastes, brackets, sealant and installation, so the quote and the site work are clear.