Fill a shallow container with room temperature water. The water needs to room temperature, otherwise the polish will harden too quickly.
Gently pour the nail polish onto the water, alternating colors as you go. Get as close to surface of the water as possible and work slowly. The polish should float, not sink.
Use a small stick to create a design in the polish. Start from the center and move quickly so the polish doesn’t start to harden.
Submerge the bottom of the glass, then pull it out and let it dry. If you see any gaps in the color, just repeat the process.