I often say, self enquiry is not a mantra. It's not something you just repeat mentally "who am i.. who am i..." it's not that sort of practice. It is an investigation, an exploration, an inquiry into the true nature of identity and the true nature of consciousness.

The inquiry/koan "Before Birth, who am I?" has a dual purpose: the elimination of all conceptual identification (ego) and to discover one's underlying radiant Consciousness, or Pure Presence/Beingness.

During my journey of self-enquiry, which spanned over two years (2008-Feb 2010), involving meditative contemplations such as “before birth, who am I?” During the process, this line of questioning, we eliminate all the candidates for my self -- I am not my hands, my legs, my name, my thoughts. They come and go and are observed, they are not me. So what am I? As John Tan said before, “you cannot know the “Ultimate Source” without the process of elimination”. What does it eliminate? The conceptual identification of self with various mentally constructed and perceived objects. This is why "before birth" is asked, as it directs the mind to this elimination. And what does that elimination reveal? Who am I, what is this radiant Being that stands alone revealed after that process of elimination?

Ramana Maharshi said:

"1. Who am I ?

The gross body which is composed of the seven humours (dhatus), I am not; the five cognitive sense organs, viz. the senses of hearing, touch, sight, taste, and smell, which apprehend their respective objects, viz. sound, touch, colour, taste, and odour, I am not; the five cognitive sense- organs, viz. the organs of speech, locomotion, grasping, excretion, and procreation, which have as their respective functions speaking, moving, grasping, excreting, and enjoying, I am not; the five vital airs, prana, etc., which perform respectively the five functions of in-breathing, etc., I am not; even the mind which thinks, I am not; the nescience too, which is endowed only with the residual impressions of objects, and in which there are no objects and no functioning’s, I am not.

2. If I am none of these, then who am I?

After negating all of the above-mentioned as ‘not this’, ‘not this’, that Awareness which alone remains - that I am.

3. What is the nature of Awareness?

The nature of Awareness is existence-consciousness-bliss"

- continue reading at https://app.box.com/s/v8r7i8ng17cxr1aoiz9ca1jychct6v84

This line of questioning (before birth, who am I?) led me to a moment in silent meditation where everything subsided, leaving only a doubtless unshakeable certainty of pure existence and presence.

So eliminating concepts until none is left with some prompting like self enquiry or zen koan will allow one to reach a complete state of stillness (stillness of the conceptual mind) and authenticate presence/clarity/radiance directly. 

While this method effectively dissolves conceptual attachments and reveals the radiant core of Consciousness, it fails to address the view of inherency and the dualities of subject and object or the deeper insight of both self and phenomena as merely nominal and overcome views that reifies the four extremes. Sometimes we call it "inherentness" in short, and inherentness means concepts being reified and mistaken as real. But that requires deeper insights and realisations and is crucial for releasing the deeper afflictive and knowledge obscurations. Merely the pausing of conceptual thinking or even revealing one's Radiance is insufficient to realise its nature. 

At this point, after radiance is realized, as John Tan points out, "before we can hop into the next path and focus on radiance and natural state, without recognizing implication of conventional and seeing through them, there will be ongoing cognitive as well as emotional obscurations. How deep and far can you go? Much less talking about natural state when one can't even distinguish what is conventional and what is ultimate."

As John Tan said before,

“When we authenticate radiance clarity directly, we have a first hand experiential taste of what is called the "ultimate free from all conceptual elaborations" but mind is not "free from conceptual elaborations".”

I also wrote some time back:

"Seeing selfness or cognizance as a subject and phenomena as objects is the fundamental elaboration that prevents the taste of appearances as radiance clarity.. then even after anatta, there are still the subtle cognitive obscurations that reified phenomena, arising and ceasing, substantial cause and effect, inherent production and so on.

So elaboration is not just coarse thinking like labelling but to me is like a veil of reification projecting and distorting radiant appearances and its nature.

Another way to put it is that the fundamental conceptual elaboration that obscures reality/suchness is to reify self and phenomena in terms of the extremes of existence and non existence through not apprehending the nature of mind/appearance.

...

If you mean just authenticate radiance clarity like I AM, then it’s just nonconceptual taste and realisation of presence.

That moment is nondual and nonconceptual and unfabricated but it doesnt mean the view of inherency is seen through. Since fundamental ignorance is untouched the radiance will continue to be distorted into a subject and object."

"The process of eradicating avidyā (ignorance) is conceived… not as a mere stopping of thought, but as the active realization of the opposite of what ignorance misconceives. Avidyā is not a mere absence of knowledge, but a specific misconception, and it must be removed by realization of its opposite. In this vein, Tsongkhapa says that one cannot get rid of the misconception of 'inherent existence' merely by stopping conceptuality any more than one can get rid of the idea that there is a demon in a darkened cave merely by trying not to think about it. Just as one must hold a lamp and see that there is no demon there, so the illumination of wisdom is needed to clear away the darkness of ignorance." - Napper, Elizabeth, 2003, p. 103"

It is important however to note that Gelug and non Gelug authors may have different definitions of conceptualities, as John Tan pointed out years ago: “Not exactly, both have some very profound points.  Mipham "conceptualities" is not only referring to symbolic layering but also self-view which is more crucial.  Mipham made it very clear and said the gelug mistake "conceptualities" as just symbolic and mental overlay, which is not what he is referring then he laid down 3 types of conceptualities.  Same for dharmakirti also...there is the gross definition and the more refine definitions.”

However, for the purpose of beginners trying to realize the I AM, just going through and focusing on self-enquiry and the process of elimination mentioned earlier is sufficient to result in Self Realisation. 

You should read this article https://www.awakeningtoreality.com/2018/12/the-direct-path-to-your-real-self.html as this author was able to bring several to the realization of I AM, and explains well the process of self enquiry and the process of elimination.