Flow arises naturally in complex, demanding professional work when each new piece of information fits coherently into a problem someone is actively engaged with solving — the same structural conditions (clear goals, a challenge matched to skill, immediate feedback on whether an approach is working) that produce flow in physical or creative activities apply just as directly to research, writing, and analysis. This matters because flow often gets associated primarily with sports or the arts, when the actual mechanism is domain-general.
The practical implication for anyone doing demanding cognitive work is that the same design principles apply: a problem broken into pieces with clear sub-goals, work structured so you can tell relatively quickly whether an approach is working, and a level of difficulty that's genuinely challenging without being so far beyond current skill that it produces anxiety instead of absorption.