We like to cut plywood on the floor using a piece of extruded foam as a backing board. It makes a nice, solid surface to make the cuts. If storing the foam board is a problem, you can cut it in ...

Cut slots for the water supply tubes. Seal the edges and face of the plywood with urethane varnish. Also check out: 11 Pitfalls of Sink Replacement. Drop in the new floor and screw it into place ...