do not approach with cross controls! Head into into wind to prevent drift (crab) as one would normally do.
Some thoughts ..
(a) either approach technique is acceptable in a crosswind although the slip approach (rather than crab) is uncomfortable for the passengers and a pain in gusty conditions
(b) during the landing it is general to align to the runway prior to and during the flare and touchdown (albeit that many larger aircraft can tolerate a moderate drift angle at touchdown .. I'm sure we have all watched with wide eyes at Boeing, and other, landing tests)
(c) if the point of the slip is to lose some height quickly the heading can be constrained according to the pilot's control inputs. Generally one would only be aligned with the runway if the aim is to correct for crosswind ... otherwise you will be slipping away from the extended centreline whether you like it or not ?
(d) anytime you are in a steady slip and controlling heading with rudder you have crossed controls
... or have I missed something along the way ?