Place the vessel sink on the washstand top as you want it to be positioned when the sink is attached.
Pencil around the base of the vessel sink, as well as the position of the drain hole of the sink.
Attach a hole bit to your drill the exact diameter as the drain hole, then cut out the drain hole through the washstand top.
Apply silicone adhesive to the top of the washstand from the pencil line you drew around the base of the vessel sink, right up to the hole you cut for the drain.
Sit the sink on top of the washstand carefully, ensuring the drain hole in the sink is perfectly aligned with the hole in the top of the washstand.
Press down gently on the sink to ensure full contact with the adhesive. Wipe away any adhesive that comes out around the edges of the sink bottom with a rag.
Leave the adhesive to set for the time recommended by the adhesive manufacturer. The washstand is now ready for positioning in the bathroom, where you can connect the plumbing to the sink.