From various traditions, I have seen the analogy of a vase used to describe the “no self”.
There is always the same space inside and outside of a vase, although that does not become obvious to us until the vase is broken. At that point, it appears as if the outside and inside space merges, and we realize it never was separate or different.
This analogy works for both forms (phases) of “no self”.
First, when we find ourselves as the Witness, as formless awareness, we see that this human self and the rest of the world of phenomena is a seamless fluid whole. There was never any separation, only the appearance of it from our previously exclusive identification as this human self. From our new “ground”, we can see it all as a seamless fluid field.
Then, the apparent separation between the Witness and the world of phenomena dissolves. There is no “I” anywhere, just what is, as it is. The temporary identification as the Witness, as formless awareness, is now revealed as just a belief in another thought. What is, is what is, beyond and embracing all polarities, including those of awareness and matter, the unchanging and changing, one and many, and so on.
What this old analogy does not mention, is that we need to construct the vase before destroying it. We need to build it, familiarize ourselves with it, and then allow it to break and reveal the undivided space which was always there. That is the whole game.
As Ken Wilber points out, it is a case of transcend and include. As we move beyond our current level, some structures remain and are included in future developments, while other aspects are left behind/transformed.
We construct an identity as a human being, and learn to function effectively in the world. Then, we construct an identity as formless awareness and learn to function in the world in that way (deepening into liberation). Then, we learn to function even with no “I” anywhere.
And at this point, we of course continue to make use of what we developed at the previous phases. We can still function effectively in the world, and we are still very much aware of the “ground” of formless awareness. The only difference is that there is no “I” located anywhere, there is no sense of (a separate) subject or object anymore.