Is this a new top? If so, and you hard mount the sink with adhesive, you'll void the warranty on the Corian because DuPont will not stand behind mounting other products to their countertops. If it's an old top and you don't care about the warranty I would use Corian adhesive to glue them together. Make sure the sink top is smooth and clean. Clean it with alcohol before gluing it on, then clamp with spring clamps all the way around while the adhesive cures.