Preheat your oven to 350 degrees F. In a small bowl, whisk together the brown sugar, salt, black pepper, and crushed red pepper. Rub the mixture all over the pork belly, pressing it in to adhere. Set aside.
Heat the olive oil in a large oven-safe dutch oven over medium-high heat. Add the pork belly and sear it on all sides until brown, about 15 minutes total. Add the carrots, celery, garlic and beer. Season with salt and place i in the oven, uncovered. Bake for about 2 hours or until the pork belly is tender.
Once your pork belly is in the oven, prepare your broth. Combine all of the ingredients for the broth in a large stock pot over medium high heat. Bring it to a boil and then reduce it to a simmer. Cover and cook for 1 1/2 hours. After the broth has simmered, strain it through a colander into a bowl and return it to the stockpot to keep warm until you are ready to serve.
Remove from the oven and transfer to a cutting board. Cover it loosely with a foil and let it rest for about 30 minutes. Slice it once it has rested.
Assemble your ramen noodle bowls, by layering pork belly, carrots, ramen noodles and green onions in 4-6 shallow bowls. Pour the broth on top and sprinkle with fresh cilantro.
Serve immediately and enjoy!