First it might be helpful to describe selfing from this particular context, which can be grouped into multiple layers that I call fetters, or something.
In the simplest terms, a fetter is a mental shackle or a psychological bond. It’s not a physical thing. A fetter is a powerful, unconscious pattern of mind that ties you to a limited self-perspective in a closed container of sensory experiences.
As such, self-identity always follows the contours of separating the self-idea from the world. From this separation spawns an experiencer and simultaneously what they experience — they both arise together simultaneously. The self belief creates the experiencer and the experience, and your inner world is given to you in two parts (subject/object or the knower and the known).
The strain is in the persistent need to keep these parts separated, (sometimes called suffering) which is simply what fetter inquiry is about: looking specifically into the various layers of straining that seem to tether an experiencer to an experience.
So, this division of consciousness could be said to be an innocent misperception. There’s no one looking through my eyes at this laptop, but there is the conditioning by which this person can function. When I refer to ‘my’ eyes, this is used as a figure of speech, a convenient placeholder which allows me to function in a sensory world. When I refer back to memories of a self, it is clear also that, although it appeared to operate as a separate individual, this was simply just the One divided into two: subject and object, but I don’t have any qualifier for what the One is, and I certainly don’t mean Oneness! As you can probably gather, using language is to describe this is very problematic.
One could say it is unconditioned, because there are no objects of knowledge that can define it. It doesn’t have a shape, a colour, a context, a smell; it doesn’t have any spatial dimensions like length, breath, width, and it has no sense that time is passing by, yet it does not exclude the physical reality — all things seemingly appear as it, including relativistic time and space, and a conventional, functional self. However, it itself is not a container of all things; it doesn’t have a perimeter, nor a top or a bottom. It is boundless, yet it doesn’t stretch itself throughout space to fit into the definition of ‘boundlessness.’
No self does not mean you merge into the environment and disappear. That is a type of severe global unconsciousness. There must still exist the ability to define the physical world and its objects. Confusingly, although no self can be described with terms like centrlessness or having no sense of inside and outside, a centre does re-emerge, but in a very different and paradoxical way. If it doesn’t, you're probably stuck in some limbo state. That centre is the ground of your reality. It looks through the eyes, becomes coloured by your conditioning, and performs various roles in the world.
The "knowing" of this is a direct connection with the totality or the timeless ground of being, but this is not a conceptual knowing. It is something that lives and endures underneath the eternal flux of life and humanity. It simply never changes, does not demand anything, has no taste, smell or shape, yet is the fundamental ground of all reality. Without it, the universe could not display its manifold shapes and colours.
So, what remains cannot be qualified, but you could say it is the uniter of all things from the miniscule field of atoms, to the vast swirling galaxies, and all the things in-between, like the arising of thoughts, and the mundane reality of human life. It’s how experience itself can happen. Without this elemental uniter, nothing can be of itself.
Why it is, nobody knows and nobody can answer.
It just is.
Once found, all questions about it cease. It doesn’t need to be qualified, theorized, conjectured or worshipped. In a sense, it evades the changing times — it has been the same uniter since time immemorial.
Living within a self identity is to limit your view to a very small region of this totality. Breaking through is to see - and live - a far greater reality. Maybe you’ll like it, maybe you won’t.
If no-self had a definition, this would come close to it, although it doesn’t hit it precisely. There are simply no words that can describe it. It is not even no-self, because this implies that there was once a self.
No-self does not mean that you lose your ability to function as a human - hence, there still remains a functional self, which consists of a multitude of daily roles. It’s not a rigid identity, but a flexible, malleable process. It’s the flow of life with all of its trials and tribulations, and its glories and triumphs.