Cut the cabbage lengthwise into quarters through the stem. Remove the cores, then slice each section into 2 inch wide strips.

Place the cabbage in a large bowl and sprinkle with the salt. Use your hands to gently massage the salt into the leaves until they begin to soften. Add enough water to fully cover the cabbage. Place a plate on top and weigh it down with something heavy. Let it sit for 1 to 2 hours.

Rinse the cabbage under cold water three times to remove excess salt. Let it drain in a colander for 15 to 20 minutes.

In a clean bowl, make the spice paste. Mix the garlic, ginger, sugar, and fish sauce (or shrimp paste or water) until smooth. Stir in the gochugaru based on how spicy you want it.

Gently squeeze any extra water from the cabbage and add it to the bowl with the paste. Add the radish and scallions.

Using your hands, mix everything together until the vegetables are fully coated with the paste. Wearing gloves helps protect your hands from the spice.

Pack the kimchi into a clean 1 quart jar. Press it down firmly until the liquid rises and covers the vegetables. Leave about 1 inch of space at the top, then seal the jar.

Place the jar on a plate to catch any overflow. Let it sit at cool room temperature, away from direct sunlight, for 1 to 5 days. You may notice bubbles forming as it ferments.

Check the kimchi once a day. Open the jar and press the vegetables down so they stay under the liquid. Taste a little each day. When it reaches a flavor you like, move it to the refrigerator. It will taste even better after another week or two.