"What is the best and more importantly, the safest method for crosswind landings - slip, crab or a combo of the two?" - Don J.
“The best method, in my opinion, is a combination of a crab on short final with a transition to a side slip in the landing flare. The side slip allows the pilot to align the longitudinal axis of the aircraft with the runway centerline, preventing side loading of the landing gear.
Practical test standards for both private and commercial require that the longitudinal axis of the aircraft be aligned with the centerline of the runway – this can only be accomplish using a side slip.
To do good crosswind landings requires practice. Start with gentle crosswinds (approximately 5 knots) until you develop your technique. Also, make a point of practicing crosswinds from both sides. Some pilots become very good handling crosswinds from one side or the other only because their home airport has prevailing winds from one side only. Seek out opportunities to practice crosswinds from both sides.”