In those moments the awareness of time disappears, and hours seem to flash by without our noticing. That is flow. When I read this description, I knew immediately what he was talking about. It turns out that watching TV is not at all a flowful activity. It seems that TV's main virtue is that it occupies the mind undemandingly.
Flow is hard to achieve without effort.
Some activities lend themselves to flow. Immediate feedback, commensurate challenges and skills, and clear goals are all precursors to flow. Lack of these makes flow difficult to achieve. Some people are inclined to flow. They set goals even when apparently doing nothing, and are able to focus their attention easily.