That’s my thinking too. Flow feels more like a result. Effort and mindfulness being what gets you there.
Though, I must concede that I hesitate to say that “Samādhi” = “Flow.” The concept of “Flow” might be broader than “Samādhi” - covering, as it does, many mundane (though pleasurable!) states of consciousness. Certain Pāli-thumping theologians will scoff at deigning “Flow” (or any Western concept!) “equivalent” to something as exalted (read: exotic) as “samādhi” … so I have to be careful what I commit to in public! 
I hope you understand
[PS: For an example of what I mean, just look at all the flak (a hundred replies and counting) Bhante Sujato is getting for translating nibbāna at all! ]