Rinse the napa leaves and add to a large bowl with enough water to cover the leaves, add 3 tbs sea salt, and let brine for 1 hour, turning over every 15 minutes to mix.
Mix the gochugaru/ginger/garlic/sugar/anchovy paste (if using) into a chunky paste.
After brining, thoroughly rinse and drain the napa leaves, gently squeeze out excess water.
Rub the pepper paste onto the surface of the napa leaves, green onion, and apple and carrot (if using), mixing well.
Add to Kimchi crock and seal with water, or a large mason jar and slightly vent lid, Let ferment at room temperature for 1-2 days before enjoying, although sooner is OK. Keeps at room temperature for at least a week, longer in the refrigerator (seal well to contain the smell).