What do you actually know?
There is present Oneness - undivided Reality. That's already the case. Reality is nondual. It doesn't need to be reached. It doesn't need to be MADE nondual.
That present Oneness is conceptually divided beginning with the knowledge of existence - I AM - as soon as that recognition that you exist comes - it's a conceptual division. I AM cannot be grasped by the mind as Oneness or Wholeness - therefore all that is NOT ME comes in as imagination. That imagining is the root of limitation, lack, because to assert something other is to limit what you are.
Then there must be a quantification of reality - we must know what it is. We must define it, label it. So present reality is divided conceptually - we call it sensation/perception. Experience. And an experience must have an experienc-er. Therefore reality is given an equation to make sense of it - subject/object.
That is an object and "I" am the subject.
That "I" then must be defined. What is it? Imagination must be used to say. That "I" is a person, a soul or spirit, an entity which came as part and parcel of this body-mind.
But wait - what is the body or mind? We haven't yet defined them. This nondual reality must be sliced and diced even further to make some intellectual sense of it. There are present sensations - experiences - a bundle of feelings - THAT must be the body. There are various patterns - language - those are "thoughts". We've now given a label, a name, a way of making it more comfortable because now we believe we know what it is. It's no longer a mystery. It makes intellectual sense.
So here we are, persons living in this body-mind, living in a world of things. Now we're comfortable - we have it all figured out. But along with these definitions, these quantifications, these translations of reality, there is by default a sense of limitation. To define yourself this way naturally creates a division or limitation - you limit yourself by all that you are not.
So the spiritual search comes - now we want to find out what we are - we've long-since forgotten it was all conceptual, all imagination in order to make sense of it, to wrap borders around everything to obscure the inherent mystery and stillness. We want to BECOME whole, because AS a thing, a defined entity, we are not whole.
But we cannot BECOME it. It was always only imagination. It was always only conceptual, a translation, an interpretation of nondual reality.
Reality is already nondual. There is no making it so. In applying any definition or concept there is a concurrent limitation imposed. Simply recognize this inclination to describe reality.
Seeking nonduality is absurd. What form or practice can change the inherent nature of reality? What experience can reveal Oneness when an experience is by definition the opposite of Oneness?
What you are seeking is already the case. Can there ever be a point when the individual person finds Oneness? It's an impossibility. The person is a product of imagination.