Why does time vanish when a task is exactly hard enough?
The moments you forget the clock, forget yourself, and just do the thing - those land in a narrow band where the task is hard enough to stretch you but not so hard it scares you.
Flow is the state of full absorption where action and awareness merge and the sense of time slips away. It does not strike at random. It shows up when the challenge of a task roughly matches your skill. Too hard for your skill and you tip into anxiety; too easy and you slide into boredom. The pull into the zone lives at the balance point between the two.
A game on easy mode bores you and you check your phone; on nightmare mode you rage-quit; on the setting that just barely beats you, two hours disappear without a blink.
To get absorbed, tune the difficulty - nudge a task up when it bores you and break it down when it scares you, until it sits just above your current skill.
If work feels like a slog or a panic, the fix is usually the difficulty, not your willpower - adjust the challenge to match your skill and absorption follows.
Flow = challenge meets skill: too high is fear, too low is yawn, dead center is the zone.
Learn the idea and practice English at the same time.