Super easy. 1 VCO gets its output “a little bit” modified by a random source and a reverb filter wisley used. The result is an oddly satifying background “forest like” noise and a shifted double voicing. Another waveform from the same VCO is taken, bended a bit and used as nifty “chirp-ish” addon as fake third voice. A kind of electronic bird for this oniric electronic forest! All with one VCO.
UPDATED! I used “some” buffers to improve the creepiness! ;-)

This is the preset for the VALLEY PLATEAU plugin: just decompress it in the PRESET folder of VCV Rack. How cool is that? ;-P
Attachment Plateau_double_delay.zip