I see there to be 3 methods:
1. Slip final through the flare & hold off until both mainwheels are on the ground
2. Crab final through the flare & hold off, yaw in flat turn to align the aircraft a bare instant before both mainwheels touchdown.
3. Combination: Crab final until at some point a transition to a slip is made, leading to a slipped landing. Where that transition is can vary. Some start it prior to the flare - even a few hundred feet AGL - others as they flare, and yet others just prior to landing as an addition to the crab method.
My preference is a combination technique, starting the yaw & wing down as I flare. I don't like a slipped final because of the added drag (unless I want extra drag for some reason) and unpleasant side forces for my pax. I found that a pure crab method relied too much on a precision timing and if misjudged resulted in either landing still with some crab not yet removed, or a drift starting if slightly early and needing some wing down anyway to prevent the drift. A gust could also interfere with the timing and need some wing down anyway.
In Islanders in Shetland the rate of yaw just wasn't sufficient to allow a crab only method to work in the really strong winds (gale, strong gale & storm force). By the time the aircraft was part way aligned it would start to drift. Even using asymmetric power to increase the yaw rate wasn't always sufficient. The end result was that I'd yaw at max rate just before touchdown (with asymm. power if needed) while lowering a wing to counter the immediately developing drift.