1. analyze the work up to the minute details, and listen to good recordings.
2. memorize measure by measure, hand by hand, then together. concentrate on small details of your theoretical analysis like intervals, notes, rhythm, etc.
3. start building blocks with those memorized measures. memorize section by section/page by page. now concentrate on the harmonies.
4. start connecting those sections/pages and memorize the whole movement/piece. concentrate on the form this time.
5. close the piano and play on the lid from beginning to end.

6. REVIEW3X... the next day, before working on new measures, review things which u memorized the day before. it's like writing with a pencil on the same spot. once is not so dark, twice is darker, thrice is even darker, and so on and so forth until the paper is torn. you would wanna get to that point where you tear up the paper to be really secure with your memory of the music.

besides, every minute you let go of them, they simply slip away too.
this may appear to be a long process. but in the long run, it's faster.
It works better and faster for me to make it a habit to perfectly memorize one measure before going to the next because i wouldn't wanna deal with loopholes later on, especially when they begin to pile up (so annoying and this is the one that takes time)... then it'd be like i would have to relearn the whole thing again.
i also work on the technique while memorizing.
of course, i can't start figuring out which technique to use if i have not the perfect musical concept of the whole piece... how it should sound, etc.
memory, technique and the music itself cannot be separated during a practice session. besides they also help one another.

N.B. This is just my personal way of doing it.

you might get ideas from it but it does not necessarily work for everyone.
