|Zazen is the only essential spiritual practice.|
Then the whole practice is to remain as awareness, which is aware of itself. You could accompany this being aware with the question: "What am I?". This question emphasizes the empty nature of awareness and denies our commonly held believe that we know who we are, when in fact our true self has none of the qualities we attribute to our self.
Sitting in Zazen is therefore an exercise of remaining aware of the nothingness that it is. Over time this will increase our capacity to stay in this clear state of mind and detachment naturally develops. A detachment from the false self which we identify with.
Even though this practice sounds simple, it has many nuances and should be evaluated and discussed regularly with a teacher to avoid the various traps of wrong practice. For example, it is easily possible to do ones daily practice in a state of day-dreaming, where one is almost entirely absorbed in thoughts about ones life. Which actually achieves the opposite of what Zazen practice is about.
To start the practice of Zazen it can be helpful to choose an object in ones experiences to focus on. This will train the ability to concentrate without interruption for extended periods of time. In my own practice I have found constant objects, like sensations to be best to develop this concentration. I start out every meditation practice with about 10 minutes of concentration on the sensation of my hands which lie on top of each other in my lap. This concentration requires effort and silences the mind. When I feel that my concentration has deepened and lengthened, I shift over to concentration on awareness without objects. Remaining aware as awareness of itself, as mentioned in the beginning.
I wish you much success with your own meditation practice. Please feel free to ask any questions you may have in the comments, or book a Consultation with me, if you want to discuss your progress in detail.