There is a lot of excess fat on pork belly. It's supposed to be there! But there will also be enough to cut off about ¼ cup worth. Dice the excess fat into cubes and render or melt the fat in a dutch oven over medium high heat. Meanwhile, toss the strips of pork belly with the sea salt, coconut sugar, cumin and black pepper in a bowl.
Using 2 Tbsp of the rendered fat, sear all sides of the pork belly over medium high heat until golden brown and set aside.
Add the onions and garlic to the pan and cook until the onions start to get soft. Pour in the apple cider vinegar and using a wooden spoon scrape the bottom of the pan (this is called deglazing) to get all the little bits unstuck from the bottom. Put the pork back in the pot along with the stock and bring to a boil. Add the bay leaves, cinnamon, oregano, and chipotle, cover, and reduce heat down to a simmer for 1 hour. Remove the pork belly to cool and strain out the onions, garlic, and chipotle pepper and set aside.
Heat a large frying pan or cast iron skillet with your oil of choice over medium high heat. Toss the pork belly in the tapioca starch and sear all sides until lightly brown and crispy. Serve pork belly in warmed tortillas with salsa, avocado cream, and pickled onions.