I am not a teacher, but anyway...
First of all, this is good (and must) for slow practice.
The idea is to use the gravity. BTW, the shoulder and elbow should also be involved in a similar fashion (but to a lesser degree), the whole arm should play.
When you hit a note, you let the weight of the whole arm help the finger, instead of having the wrist and elbow tense and hitting the key just by pushing finger down into the key.
The wrist is relaxed, the finger hits the key, and the wrist and elbow continues to move down until there is time to stop the movement..
When you release the key, you move the wrist (and elbow) up first, with finger laying down on the key, and the finger follows the wrist up naturally to release the key.
Think of this as something similar to the arm movement of swans from The Swan Lake, but less pronounced, and with less shoulder movement.