Add dried chiles to a large heavy-bottomed Dutch oven or stock pot and cook over medium-high heat, stirring frequently, until slightly darkened with intense, roasted aroma, 2 to 5 minutes. Do not allow to smoke. Add chicken stock, raisins, orange juice concentrate, chipotles in adobo, white vinegar, and fish sauce. Bring to a boil over high heat, reduce to a bare simmer, and let cook until chiles are totally softened, about 15 minutes. Blend into a smooth puree using an immersion blender or by transferring to a countertop blender. Set aside.

Carefully pat pork cubes dry with paper towels or a clean kitchen towel. Heat vegetable oil in a large heavy-bottomed Dutch oven over high heat until smoking. Add pork all at once and spread evenly over the bottom surface. Cook without moving until the bottom surface is well browned, about 8 minutes. Transfer pork to a cutting board and set aside. Add onions and garlic to Dutch oven and cook, stirring frequently, until softened and beginning to brown, about 10 minutes. Add oregano and cumin and cook, stirring constantly, until fragrant, about 30 seconds.

Add chile mixture to Dutch oven and stir to scrape up any browned bits from the bottom. Add bay leaves along with the pork and any accumulated juices. Bring to a boil then reduce to a bare simmer. Cover, leaving lid slightly ajar, and cook, stirring occasionally until pork chunks break apart when you apply pressure with a spoon, about 2 hours.

Sauce should be thick, with an almost ketchup-like consistency. If too thin, increase heat to a light simmer and cook, stirring frequently, until reduced to the desired consistency. Season to taste with salt.

Serve pork with corn tortillas, cilantro, diced onions, lime wedges, and queso fresco. Pork can be stored in a sealed container in the fridge for up to 5 days.