Flowtime Technique was created by Dionatan Moura in 2015, published in his book The Mantra of Productivity in 2016 (currently only in Portuguese).
Flowtime is a focus-oriented period of time. The duration of a Flowtime starts between 10 and 90 minutes, being extended or not according to your focus. When this period of time is over, you decide if your Flowtime can keep on. Just ask yourself if you still have focus enough to continue doing your tasks. If you feel you can be focused more some minutes, add these minutes to your Flowtime in an alarm. If you are not able to be focused, take a break. You decide how much time you need to recover your focus. Maybe a short break, maybe a long break.
For example, you decide to run a Flowtime of 45 minutes. You set an alarm for 45 minutes and start doing your tasks. When the period of time ends, you ask yourself “For how long minutes more will I stay focused on my tasks?”. If it is zero minutes, take a break. If it is 15 minutes, set an alarm for 15 minutes and keep on your Flowtime (45+15). When the period ends, ask again yourself if you can stay focused more time.