Traditional Kimchi

Trim the core ends of the cabbage off. Cut a short slit in the base of the cabbage, enough to get a grip on either half, and then gently pull the halves apart so the cabbage splits open. (For large heads of cabbage, I cut into quarter wedges.)
Cut a slit through the core of each half, 2 inches above the stem. You want the cabbage leaves to be loose but still attached to the core.
Dunk the halves in a large basin of water to get them wet. Sprinkle the salt between the leaves by lifting up every leaf and getting salt in there. Use more salt closer to the stems, where the leaves are thicker.
Let the cabbages rest for 2 hours. Turn over every 30 minutes, so they get well salted. From time to time you can ladle some of the salty water from the bottom of the basin over top of the cabbages if you want to.
After 2 hours, wash the cabbage halves a few times under cold running water. Giving them a good washing, to remove the salt and any dirt.
As you wash, split the halves into quarters along the slits you cut into earlier. Trim off the cores, and put them in a strainer over a basin so they can drain well.

Combine the water and the glutinous rice flour in a small pot. Mix well with a wooden spoon and let it cook over medium heat for about 10 minutes until it starts to bubble. Add the sugar and cook 1 more minute, stirring. Remove from the heat and let it cool off completely.
Pour cooled porridge into a large mixing bowl.
Measure out the fermented salted shrimp, squeeze the liquid into the bowl, then finely mince the shrimp, adding to the porridge.
Add the garlic, ginger, and onion to a small food processor and make a puree. Add to the porridge.
Add the fish sauce and desired amount of hot pepper flakes. Mix well with the wooden spoon until the mixture turns into a thin paste.

Spread some kimchi paste on each cabbage leaf.
When every leaf in a quarter is covered with paste, wrap it around itself into a small packet.
Put into your jar, BPA-free plastic container, or onggi (traditional kimchi pot) and make sure to press down so that the air bubbles are squeezed out..
Set aside for 2-3 days to ferment (make sure to set some aside to eat right away! It's delicious!) You'll know when it's doing it's job, when you press down and there are small bubbles.
When you get those bubbles, stick into the fridge for keeping.