1. In a large mixing bowl, combine chopped Napa cabbage and salt. Massage the salt into the cabbage leaves and let it sit for 10 minutes.
2. Rinse the cabbage thoroughly to remove excess salt and drain well.
3. Add carrots, daikon radish, garlic, ginger, fish sauce, Thai chili flakes, and green onions to the bowl with the cabbage. Mix well.
4. Pack the mixture tightly into a fermentation jar, pressing down to remove air bubbles.
5. Seal the jar and let it ferment at room temperature for 24 hours. After 24 hours, transfer to the refrigerator and let it ferment for at least another 3 days before serving.