Remove the stems and seeds from the ancho, guajillo, and arbol chiles. Heat a skillet over medium heat and toast the chilies for about 1-2 minutes on each side until they become fragrant. Be careful not to burn them.

Place the toasted chiles in a bowl and cover with hot water. Let them soak for about 20 minutes until they are softened. Once softened, drain the chilies and blend them with 1 cup of beef stock until it forms a smooth paste. Set aside.

Season the chuck roast pieces generously with salt and pepper. In a large skillet, heat the vegetable oil over medium-high heat. Sear the meat in batches until browned on all sides. Transfer the browned meat to your slow cooker.

In the same skillet, add the minced garlic and diced onion. Sauté until the onion becomes translucent. Add the cumin, oregano, and optional smoked paprika. Stir to combine and cook for another minute.

Pour in the chili paste and the remaining 1 cup of beef stock, scraping the bottom of the skillet to release any browned bits. Bring the mixture to a simmer and then pour it over the meat in the slow cooker.

Add the apple cider vinegar to the slow cooker and stir everything together. Cover and cook on low for 7-8 hours or on high for 4-5 hours, until the meat is tender and the flavors have melded together.

Taste the chili and adjust seasoning with salt and pepper if necessary.

Serve the Chili Colorado garnished with fresh chopped cilantro.