Use thick shelves (¾" minimum), add vertical supports every 24–36 inches, and reinforce with metal brackets or a solid back panel.

Turn off water supply, disconnect plumbing, remove the old vanity, and install the new one level on the floor. Reconnect plumbing and seal gaps with silicone caulk.

Install hidden shelf brackets or build a ledger board secured to wall studs. Use thick, sturdy materials to prevent drooping over time.