Ease is what a hard thing feels like from the inside once you have done it enough times. Ask somebody how they produced that in an afternoon and they often cannot tell you. The difficult parts have gone quiet and stopped being visible even to them.
So effortlessness is not the opposite of work. It is a late stage of it, invisible from outside, which is why everyone assumes the people who have reached it were born there.
Whatever costs you a whole day at the moment has a version of itself that will one day cost an hour, and you will not notice the transition happening.