Cut the napa cabbage into quarters, removing the hard stem at the bottom. Roughly chop the cabbage and set aside in a large bowl. Add the sea salt and water and mix well, pressing down to ensure all of the cabbage pieces are covered in the salt water. Set aside for 1 hour and 20 minutes, mixing once or twice during that time.
Rinse the cabbage well to ensure the salt water is completely removed and set aside in a colander for 10 minutes until dry. Add the sliced spring onions and mix.
In a large bowl, combine the gochugaru, garlic & ginger paste, fish sauce, light soy sauce, sesame oil, orange marmalade & toasted sesame seeds. Mix well.
Mix the prepared vegetables and spice paste. Mix well until all of the vegetable pieces are coated. Spoon the geotjeori into a large clean jar and set aside in the fridge. The geotjeori is ready to eat immediately but will taste best after 24 hours.