One reaches flow in activities where ... "a sense that one's skills are adequate to cope with the challenges at hand, in a goal-directed, rule-bound action system that provides clear clues as to how well one is performing."
This quote demonstrates several truths that are the hallmark of quality learning experiences.
First, the learner must believe that she has the skill to meet the challenge so a) there must be some challenge and b) the challenge cannot be so great that the learner doesn't believe that she can attain the goal.
Second, sufficient structure must be provided so that the learner can navigate the activity with a certain degree of certainty.
Finally, feedback must be connected to the goal that one is pursuing and must be explicit in describing the current performance against the ideal state.
Does this square with your beliefs about what quality teaching and learning looks like?