To make kimchi, first, cut the cabbage lengthwise into quarters, through the stem. From each of the pieces then cut the cores. Ensure that you cut each quarter cross wise to strips that are not less than 2-inch in width. 

In a large bowl, place the cabbage and sprinkle salt all over it. Use your hands to mix the salt properly until it begins to soften a bit. Now, add enough water to it until the cabbage is properly covered. Place a plate on top of the cabbage and weigh it down with something heavy. Allow it to stand like that for one or two hours.

Ensure that the cabbage is rinsed properly in cold water at least three times. Keep it aside to drain it in a colander for about 15-20 minutes. In the meantime, start to prepare the spice paste.

To make the spice paste, first, properly rinse and dry the bowl you will use for salting. Then add the sugar, fish sauce, shrimp paste, ginger, garlic or water and stir into a smooth paste. To it, add the red pepper/chili flakes and stir properly. If you want it mild, add just a tablespoon of it. If you want it to be spicy, add 5 tablespoons of it. Once ready, keep it aside until the cabbage is ready. 

Once the cabbage is ready, gently squeeze out any water, if remaining, from the cabbage and add it to the spice paste. To this add the scallions and mix well. 

Gently work the paste using your hands and let it seep into the vegetables until it is properly coated. 

Once ready, take a 1-quart jar and pack the kimchi in it. Press it down until the liquid that comes out of the kimchi rises to cover the vegetables, leaving at least an inch of space on the top. Seal the jar, once done. 

Allow the jar to stand at cool room temperature, far away from direct sunlight, for anywhere between 1 and 5 days. You may see bubbles inside the jar and brine (which is the liquid of the kimchi) may seep out of the lid.

Keep checking the kimchi atleast once a day, opening the jar and pressing down on the vegetables with a clean finger or spoon. This way the vegetables will be submerged under the brine. Allow it to ferment properly and keep checking the taste from time to time. When the kimchi tastes ripe enough, put it in a jar inside the refrigerator. Either you eat it right away, or keep it inside an airtight container inside the refrigerator for another week or two.