Once you have three or four genuine flow moments, look for the pattern. Not the industry, not the job title — the verb underneath. Were you untangling something? Bringing people together? Making order out of mess? Explaining a hard thing simply?
The recurring verb is the thread. It tends to survive every career change, which is what makes it such a dependable guide: it points, quietly, at where your next flow moment is most likely to be. This is close to what Cal Newport found studying people who love their work — passion tends to follow deep engagement and mastery, rather than arriving first and leading the way.