With the vanity top removed you can now easily access the inside of the sink base cabinet. You need to check the perimeter of the base cabinet and find out where it is attached to the wall. You'll find either screws or nails. These need to be removed.
- Remove any screws attaching the base cabinet to the wall.
- If the base cabinet is attached by nails, use a pry-bar to get under the nail and gain the leverage needed for removal. You can also try the claw end of a hammer but it may be difficult to get the claw edge under the nail head.
- Once the fasteners are removed, the sink base is easily removed from the wall.