I don't think it's common for people to wait for flow to come in order to get things done. You can set up the conditions for it and likely reliable trigger it, but getting things done (or concentrating on a problem) is how you get to flow in the first place.
You might be in the flow state without knowing. :)
I'm positive you experience "flow" all the time, maybe without realising it. It's not the magical experience you may think it is, just a state of being focused on work. You don't have to actively work on getting into "flow", it just happens naturally when you're working undisturbed for several minutes on something you understand.
>Instead I try and use what I call "micro-progress", where you try and identify the smallest thing you can do to move the task forward, and do it.
That sounds like a great way to focus (and get into "flow").
Oh, the way people sometimes talk about it, I really thought it must be some amazing feeling, and I'd definitely know if I'd experienced it! I'm slightly disappointed now.
I'm not sure either. I definitely remember occasionally feeling a distinct "flow" feeling the first few years I was studying and working. But now I still have periods of similar and superior concentration, but it's not accompanied by any extraordinary feeling.
I'm not even sure nowadays if I really experienced this, or if the feeling is just nostalgia.
Instead I try and use what I call "micro-progress", where you try and identify the smallest thing you can do to move the task forward, and do it.
Maybe one day I will experience flow, but in the meantime I'm fine without it.
p.s. unrelated, but another thing I have no experience of is ASMR.