Now to bounce off this. I think that there may actually be a difference between what this practice can do for you and the experience of being in the flow. However, I think they are closely related. My idea of what it means to be the flow, you are, in a sense, not acting from your conscious "I" mind, but just kind of acting without acting. This is the whole Taoist Wu-Wei concept. But really, you are coming from the space from which thought arises, rather than the thought itself.
So when you are in the flow with coding, swim, or bike ride, you are in the midst of an action that granted you access to this state. But you did not actually consciously enter this directly state by choice.
But the I think the trap can be that you can only access this when you are doing things that lead to being in the flow. What about being able to enter this state when you are really upset about something or when things are going badly, or when you are bored, or when you are doing something compulsively.
The practice I believe is trying to access this state at random times of the day, and especially in those times when you are not engaged in an activity that lends itself to this awareness, but actually engaged in activities that do the opposite (such as being annoyed at someone).
The idea is that you are building this muscle that allows you to access the "flow" more and more and eventually maybe realize that in some way can always access the space from which thought arises, because that space must always exist.
But again, this is theory. Practice is hard. I'll take a moment now.
The concept for this came from this ebook. I've only skimmed it.