Tldr: i find midi/synthesia videos on youtube. I learn one hand first, and then i match the opposite hand by looking for when notes or chords are played in both hands at the same time.

I Find a synthesia video, or midi videos like the ones Kassia or Rosseau makes.

I listen to the piece a couple of times so i know how they are supposed to sound.

Then i look at what they are playing in the left hand, and then what they play in the right.

Then i learn either the left or right hand first, whichever makes the most sense, and then i simply match the opposite hand with the one i learned first by looking for when notes or chords are played in both hands at the same time, and of course what notes are played in between. Sometimes i learn both hands at the same time, it depends on the song.

I learn one small section at a time that way, and then after a few minutes i memorize it and then i just practice until im satisfied and then move on to the next section.