Soak the ox bones in water over night in the refrigerator. This is to remove as much blood as possible from the bones.
After draining, put the bones in a large stock pot and cover them with water. Bring to a boil. You will see scum floating to the surface. After 10 minutes of par boiling, remove from heat and drain completely.
Wash the bones thoroughly so that there is no more scum left.
Clean the pot and add the bones back in. Cover with water, then bring it to a medium boil (covered) for 6 hours.
Check on the water level from time to time during these 6 hours. You will need to add more water as it evaporates. After a few hours, the broth should be a nice milky color.
After 6 hours, remove from heat and strain the broth into a large bowl. Set it aside to cool down completely before storing it in the refrigerator.
Remove the meat on the bones and set it aside. Put the bones back into the stock pot and cover with water again.
Put the meat into a blender with a little of the stockpot water. Blend until smooth.
Bring to a medium boil, add the blended meat, and cover for another 6 hours.
At the 2 hour mark, soak the brisket in cold water for 1 hour.
After 1 hour, add the brisket to the stock pot for the remaining three hours.
When the 6 hours are up, remove the brisket and set it aside to cool down completely before storing it in the fridge for later.
Drain the broth into the large bowl of broth from before. Make sure to use a fine strainer since this batch will have blended meat chunks. Let it cool completely before putting it back in the fridge.
Put the bones back into the pot and cover with water again. Boil covered on medium heat for another 6 hours, adding water as needed (this time not too much). You may skip this boil or shorten the time if you want to. I recommend not skipping it. You can throw away the bones after this.
Drain the broth once more, let it cool down, and put it back in the refrigerator until the fat solidifies at the top.
Remove the layer of fat at the top and discard it.
Reheat the amount you will use of the gelatinous broth. You can store the rest in the freezer for later use.
While the broth is boiling, thinly slice the brisket. The thinner the better!
To assemble a bowl, add some cooked rice and somyeon noodles. Put the brisket slices on top.
Ladle over some broth
Season with salt and pepper to taste, then add chopped green onions