Focus on the flutter, it is like a metronome. Don't let your thoughts wander, just focus on the flutter and let it guide your brain down to a slower frequency.
This audio goes from 20 Hertz down to 3 Hertz, over 30 minutes.
Say Alexa stop, to quiet the sound. Say Alexa, exit to quit.
If you only just would like to hear Ocean Waves, look for "Ocean Waves" on the Skill Store, or just say, "Alexa, NEXT."
After 30 minutes, ocean waves will play." In the absence of stereo headphones, concentrate on the flutter and it will work equally well.