The only productivity hack that i found useful is:

Having a unintrupped time in working flow.

You need to attention to the quality of the time that you have. Let's say you have about 4 hours to work on something. You must not let the time to be divided into four separate one-hour slices, or worse eight seperate thirteen minutes!

Also remember that, this is not only the matter of an hours. It can be expanded to the days. What do i mean by this?

I mean, if the task is daunting enough, it's MUCH more productive to put 2 consecutive days completely to work on that, then to do it in 2 hours everyday throughout the week.

Anything more than that, feels like an efficiency trap.

That's it.

UnRelated

This concept can be applied to any other activity as well as formal working hours. Whether it's Lifting some weights in GYM or Reading an interesting book or even spending quality time with a someone you care about.

Ask yourself: When was the last time you had three or even four completely uninterrupted hours to yourself and your work?

It might depend on the kind of work that you do, But uninterrupted time is the single best thing for quality output and genuine enjoyment that i found; for almost anything.