Obviously there's nothing new about layers in recordings, 60 years after the advent of multi-track recording. Nor is there anything new or different in ambient music, except perhaps at the level of perception.
In ambient music, the various layers can be as follows:
Constant flat line sounds (drones)
Annoying By Intention/Startling
Sounds From Outside
Annoying sounds can work if there are other layers that can float in and out of attention. Unvaried metronomic sounds without meaning or context can get tiresome. Annoying material is okay to use, but it needs variation and intermittency. (Easier said than done.)
Olafur Eliasson's waterfall installations simulate this depth perception with vision. But the ears also have depth perception for purposes of locating oneself when vision is reduced.
Perhaps a more interesting way to add variation in scale and proximity is to set up three identical tracks with different reverb settings; one for distant (300 feet), medium distance (200 feet) and 50 feet, and cross-fade them. While the ear is focusing on other things, it will also notice these changes on the periphery.
Sound layering also has an interesting analog in the cross-rhythms of African music, with each part taking turns for our attention, then zooming out so we can hear the gestalt. But listening to the whole can temporarily "tear" the fabric, as the player-as-listener can lose their place and have to merge back into the groove. This then is the rub between playing and listening: Passivity in both areas is inimical to the cohesion in the music, and ultimately to a listener. Listening is perhaps 5% of playing, yet very important feedback to the players.
We play in groups, but we also listen in groups. We tend to gravitate towards a perceptual meso-world, an equilibrium that allows simultaneous weaving in and out of layers of focus. The great focuser of attention is the excitement at the group level, when everyone merges into one shared experience--like African drumming.
Polyrhythms are typically understood as a product of interlocking parts, but they can be an emergent property of identical parts running at different tempo "layers", working in combinations with other sound layers above it.
We don't realize it, but anytime we use any type of graphics or video program that has layers or tracks we are in a geologic metaphor looking at strata in the earth's crust. There are layers below (rhythmic) and layers out to the horizon (melody and pitched elements) that give at least two dimensions for sound perception, from the "invertebrates" of a bass drum moving at a slow rate, to the "modern mammals" of a manic looped sample.