Using a knife, cut napa cabbage in half lengthwise. Cut into 1/8-inch ribbons, avoiding the core. Using a cheese grater, shred daikon and carrots. Cut green onions into thin rounds, reserving white parts.

In nonreactive container, combine cabbage, carrot, daikon, and green onion. Add large amount of salt, and toss to coat. Set aside for several hours, or as long as overnight (if salting overnight, make sure to refrigerate). This draws moisture out of the vegetables, and also kills off bad bacteria.

Transfer vegetable mix into a glass jar, leaving ½ inch of head space. Loosely cover with lid, making sure the jar is NOT sealed airtight. Leave at room temperature for 3 to 5 days. Around day 3 you should start to see tiny bubbles forming in the brine of your vegetables - this is normal. The longer you let your veggies ferment, the more tang and fizz you’ll get in the finished product.