The 4 Frames of Reference are contexts toward which you direct your attention. (7 Sets index) You just kind of zone out and focus on them. This is like a master painter contemplating his canvas and his paints. He may contemplate the colors of his paints, their texture, and so forth.
In your case you work backwards, unpainting your painting until you are contemplating the canvas, and then further until you are contemplating your not-even-the-canvas: Somehow considering the mental medium that will carry the form of the picture in the witnessing of it.
Again, you have perhaps looked at a computer or TV screen up close, seeing then the individual pixels and the pixellated fabric of the image. You might then become absorbed in the nature of the pixellated fabric itself. Or you might listen with an ear to the sounds you are hearing, the forms of the sounds, and the possibility of those forms.
Your thought itself has structure, and you can consider that structure. Beginning to pay attention to the right things is the 4 Frames of Reference set. More