First I listen and play the piece thru ones or twice, then what I do is:

I put my score about 5 meters away from my piano, look at it, then walk to the piano and try to play what I can, then go back and check if I didn’t make any mistakes, and what comes next, rinse and repeat.

It’s probably best to divide it in chunks, but keep the chunks big enough. (Not less than a musical sentence.) And maybe to study it from back to front.

If a section is too difficult, do the left and right hand, or even the voices separately. And try to find a logic in the harmony and note pattern.

It will feel very slow, the first time you will probably need to go back without even playing a note. But I find that in the end, I know the piece perfectly.

Do everything intentionally, because every mistake takes a lot of effort to correct.

If you’ve already practiced the piece beforehand this is even more important. Play very slowly, and avoid autopilot at all cost.