Since I was the one (I believe) who first mentioned flow to you, I owe you a definition of what I meant.
In general terms, it's a matter of writing the story--and the story is made up of single sentences, all strung together--so that the reading is experience is smooth and connected. This takes practice, sharp editing, and a good ear.
When writing is said to have "good flow," it means that it's all connected: sentences to sentences, paragraphs to paragraphs, scenes to scenes. Reading the story is like following a road that has no potholes, no gaps, no rough pavement. It may twist and turn and climb and dip, but it's like driving on fresh pavement all the way. A novel that has really excellent flow is one that is so tightly joined at the seams that you could scarcely remove a sentence without creating a gap, because that sentence is the bridge between the one that came before and the one that comes after. And every sentence is like that.
Sentences that flow are easy to parse, easy on the ear, and move smoothly and logically each one to the next.