You can slip, either forward or side slip in any airliner as long as you have the proper speed. All my crosswind landings in airliners were side slips to compensate for the drift, the forward slip is the same except the nose is not positioned lined up with the runway. The aerodynamics are exactly the same, one is used to compensate for crosswind and land straight, the forward slip is to cause fuselage drag to increase drag and descent rate.
I heard a story of a 737 operator doing it when idle power didn't work and landed just fine. I wouldn't advertise I did it however.
For us that use the side slip to have the plane land straight and not in a crab to not abuse the landing gear on touchdown we also know we need to have the proper speed. It is quite simple.