how to do backwards IK?

So ive rigged a model of a quadrapedal creature, and added IK to the feet so i can move them and they shift the legs only.
What i’d like to be able to do is grab the body and shift that, and instead of acting like the FK, they act like IK and the feet stay still where they are, like the creature is shifting its body weight in the same position.

they seem to be doing what i describe in this video:

How do i do this?

did you add the target?

Here is basic bone / IK setup for squatting: