Right now, there is a space of wakefulness which is obvious, maybe overlooked, but clearly obvious and present.
This space of wakefulness is the opening in which everything appears. Just look!
Not "over there" - don't try to force-fit awareness into an "outside object" - question the very concept of "over there"?
Within this immediate space, right here and now, comes sensations - body, thoughts, emotions, pain, happiness - within this space comes perceptions - trees and birds and trains and houses and dogs and cats...
Is there anything outside of this space? Does this space extend to "out there"? Is there really an "out there"? Where is that perception registering? Is that "wall" registering "over there" or right HERE?
The eyes which are seemingly the "seer" of these sights are themselves appearances IN this space!
The ears which are seemingly the "hearer" of these sounds are themselves appearances IN this space!
The thoughts and the "thinker" both appear as sensations in this space.
Any movement detected moves within the space.
Does the space move?
Any conflict endured comes and goes within this space.
Is the space conflicted?
Something remains prior to, beyond, as the ground or condition for all appearances. That "something" isn't hidden, isn't achieved, isn't learned. It's already fully present - Presence - wakefulness.
The perceptions of room, walls, the objects in the room, these words, the hands on the keyboard, the appearance of the screen, the sensation of breathing and heartbeat, the sensation of butt in the chair, the thoughts of confusion or clarity or apathy - all is presently arising and passing within this space.
It simply cannot be missed. It can be overlooked, ignored - yet this Presence, this opening, ground of Reality is the most intimate aspect of experience.
It is Beingness. It is what we really mean by "I".
Mental analysis of advaita pointers is an exercise in futility - missing the point. Simply stop and realize that no experience can possibly arise without this Opening of Knowing.
Anything gained, learned, achieved - will all be passing content and irrelevant. The space remains unaffected, not conflicted - not in need of anything - not able to lose anything.
You ARE the opening, the stage on which the World itself does it's dance called Lila, the screen on which Life sees itself, the nothingness from which everything has freedom to appear.