Prepare the Cabbage: Cut the Napa cabbage lengthwise into quarters. Remove the core and chop the cabbage into bite-sized pieces. Place them in a large mixing bowl. Salt and Soak: Sprinkle the sea salt evenly over the cabbage pieces. Toss to ensure even distribution. Allow the cabbage to sit at room temperature for 2 hours, tossing it every 30 minutes. It should wilt and release some water. Rinse and Drain: After 2 hours, rinse the cabbage thoroughly under cold running water to remove excess salt. Gently squeeze out any remaining water. Drain well.