The book is The Royal Seal of Mahamudra: Volume One: A Guidebook for the Realization of Coemergence: 1 by Khamtrul Rinpoche III (Author), Gerardo Abboud (Translator)

 Here's an excerpt on Self-Liberation:

...Similarly, regarding whatever is in the field of the tactile sense organ,

such things as fabrics that are soft or rough to the touch, this tactile

sensation itself is your own mind. Avoid slipping into grasping or rejecting.

Whether soft or rough, do not try to find the mind anywhere apart

from the softness or roughness itself, but rest at ease right there without

distraction. If a pleasant or an unpleasant feeling arises, recognize it

and rest mindfully.

Likewise all thoughts arising in the field of the mental sense organ—

right or wrong, good or bad, subtle or coarse—are also your own mind.

Avoid liking the right ones and spurning the wrong ones. No matter

what thought arises—good, bad, or neutral; subtle, tangible, or gross—

recognize its identity through awareness and sustain it naturally. If any

fixation arises, such as thinking of this and that in regard to thoughts

of right and wrong, that itself is a fixating thought. So identify that

grasping thought and rest on it at ease. In short, even when it is not the

case of good or bad thoughts but is one of stillness and movement, avoid

making choices. Do not taint with blocking or pursuing. If the mind is

still, relax on the identity of that stillness. When it is dispersed, let loose

in the identity of that dispersion. When still or when anything arises,

relax on that. Keep to the very identity of what occurs, and sustain its

continuity without clinging elsewhere to good or bad.

In fact, no matter what perception of good or bad arises in the six

sense fields—forms in the field of the eyes, sounds in the field of the

ears, smells in the field of the nose, tastes in the field of the tongue,

tactile sensations in the field of the body, or thoughts in the field of

the mind—don’t judge as good or bad, and don’t indulge in likes and

dislikes. Whatever appears, whatever arises, first identify it, then relax

and rest in that state, and finally let it be released by itself.

For us, who have been in beginningless samsara all our lives due to

very strong habits formed long ago, there is no way for thoughts of

passion and aggression not to arise; these thoughts will no doubt occur!

Determined not to slip into delusion, you must identify these thoughts

and let go directly on them. Rest in the state of knowing the nature of

the very thoughts of attachment and aversion.

Lord Gotsangpa said:

"In general, the apparent myriad of phenomena is one’s own

mind. Since phenomena and emptiness have never been

abiding as two separate entities, there is no need to restrain

cognizance within."

Also:

"When there is an appearance of a form in the field of the eyes,

that appearance of form itself is one’s mind; the apparent

form and emptiness are not two. By resting gently right on

the form without grasping, subject and object become naturally

liberated. The same applies to sounds, smells, tastes,

textures, as well as mental occurrences: by resting on the

occurrence itself, it becomes self-liberated. That is to say,

instead of meditating on cognizance, by meditating without

grasping right on the outer objects of the six sense perceptions,

the six senses arise as meditation and enhancement

will ensue."

Siddha Orgyenpa said:

"Static or mobile things of the outer world that may be seen,

including any possible inanimate object—such as earth,

stones, mountains, rocks, houses, and estates—or the diversity

of beings, both high and low, in the three spheres of

existence—such as gods and asuras, and those in the three

miserable realms—no matter what is perceived, none of these

things has even a single hair of existence as an outer entity.

They are the natural luminosity arising from the radiance of

one’s own mind.

At the time of practicing this, proceed as follows. When

inanimate things such as earth, stones, mountains, or rocks

appear, don’t go into the fixation of perceiver-and-perceived

in relation to the inanimate object. No matter how it appears,

relax loosely right on it. Avoid tainting it with hopes for good

experiences and fear of bad ones. No matter what appears,

apply the central practice on that itself. Uninterrupted by any

other thought, in that state rest loosely and at ease. Resting

in this way, you do not need to block appearances, try to

accomplish emptiness, or search elsewhere for an antidote. A

vivid union of the inanimate object and awareness is what is

called “using phenomena as the path,” “merging phenomena

and mind into one,” and “seeing the essence of indivisibility.”

By doing so you are capturing the key point of practice.

If you don’t know how to relax right on phenomena in this

way, but instead indulge by means of thought activity in a lot

of corrections intended to improve the situation, phenomena

will not arise as meditation.

Also when seeing any of the six kinds of beings—high or

low, good or evil, happy or sad—whoever it is, practice as in

the case of an inanimate object. Recognize whoever appears,

and in a state of nonmeditation, barely undistracted, rest

loose right on it. By this, phenomena and mind are indivisible.

Do not regard present appearances in terms of fault or

virtue. Avoid fabricating or modifying. Do not taint with the

intention to reject or accomplish. Take them as the practice

exactly as they are."

The method of resting should not be limited just to what we have

seen. Using the six sense perceptions as the path should be carried

out all the time as the main practice. Otherwise, although you may

somehow maintain composure during formal meditation, later when

encountering outer desirable objects of form, sound, smell, taste, or

touch, you will respond with a total lack of determination, enjoy the

sense pleasures in an ordinary way, and slip into delusion. If you turn

the wheel of passion and aggression or hope and fear, the training we

discussed will not show up when needed. You would then be neglecting

the great objective, so the crucial point and main purpose would be

absent. Rather, during the main practice of meditative composure, and

especially at all times, you should learn to use all perceptions as they

are in their own nature.

To use the six sense perceptions as the path has many purposes. The

initial effect is that you will cease to slip under the influence of the six

senses thus giving them free rein, and phenomena will no longer negatively

affect your meditation; later, phenomena will arise as ornaments;

and finally, there will be no duality between phenomena and mind, and

you will have arrived at the expanse of the great pervasiveness of the

dharmakaya.