Perfect. So the "back" part is just contraction of the hamstrings. Something like kicking one's glutes with ones heels?
Once this is done, the tips of the skis are down, the tails are up.
One more question on my mind... do you feel a "pause" and then a "fall" during the "pulling the feet back"?
I think of this moment as similar to the apex of a ball toss. That short moment should allow the upper body and head to get back forward of the feet (in combination with the "feet pullback".)
The upper body just moves in a stable line down the fall line with very little movement. So, the focus is all on the feet. If you ski in the trough, there's a lip at the end of the trough that pushes your skis up. This lip is basically the shoulder of the bump, and you have to absorb it. You can't let the lip push you too high, so you actively pull up your feet. As you pull up your feet, you're weightless. Then it's very easy to rotate the skis as the slope drops away from the tips. So, during that weightless moment, all in one motion, the feet are being pulled back, the skis are steered, knee angulation tips the skis until you load the inside edge of the outside ski tip again on the backside as shown in that still frame I captured according to Aldighieri's description. You want the ski to be rotated past the fall line before loading again. Then it's like carving with forward pressure. If you're happy with the speed, you just carve along the ski edge into the trough until you absorb the next bump. If you want more speed control, then you allow the tails to smear around on the backside as you carve with forward pressure until they slide into the trough. Once you're in the trough, there's no more smearing that can happen, so you have to get it all in on the backside.
In order to have the right "pause" and not necessarily "fall", but gradually regain pressure, you need just the right amount of absorption. That's where experience comes in. Too little, and you get tossed. Too much and all the work is coming from you, not the bump. Timing is critical.