Focus for 25 minutes. Break for 5. Repeat. Customize the durations to fit your workflow.
Before you start: Write down the task you plan to work on. Having a clear goal for each session prevents drifting between tasks.
During focus time: Close unnecessary tabs, silence your phone, and commit fully to the task. If a distracting thought pops up, jot it on a notepad and return to it during break.
During breaks: Stand up and move. Look away from your screen. The break is for your brain to rest -- do not fill it with more screen time.
After 4 sessions: Take the long break seriously. 15-30 minutes of genuine rest will make your next set of sessions significantly more productive.