Had insomia in highschool. Didn’t know what it was but taught myself guided meditation to overcome it.

For me, it was usually a song being stuck in my head. I would see myself floating up and away from the earth amd into space where the void was silent.

I also learned to pay attention to the mental “feel” I had while driftong off to sleep and pictured myself sinking into sleep like a submarine beneath the waves.

I know these aren’t super helpful descriptions because if I could really verbalise and teach it I would be doing that for a living.