pomodoro technique is cliche for a reason.

get yourself a cheap timer. make a check-list of tasks you want to get done pick the first task, set the timer for 25 minutes, and do nothing but that task. Close other windows, turn on DND, etc. when the timer goes off, take a 5 minute break (check your email/slack, go on stackernews, use the restroom, whatever). Set the timer for 25 minutes and do it all over again. Every 4 cycles, take a 20 minute break. At the end of the day you'll be shocked at how much you got done.