Bring 2 cups of the water to a boil. Place guajillo and ancho chiles in a medium-size mixing bowl, cover with boiling water, and let stand for 20 minutes to rehydrate.

While chiles are soaking, place 1-1/2 teaspoons of the vegetable oil in a dutch oven (preferably cast iron) and heat over medium-high heat for 1 minute. Add half the pork, brown, and, using a slotted spoon, transfer to a plate. Repeat with remaining oil and pork. Add onion and garlic to any pan drippings and cook for 5 minutes or until edges of onion begin to brown. Remove dutch oven from heat and set aside.

When chiles are rehydrated, remove from water (discard water). Remove stems, seeds, and membranes from chiles. Wear rubber or plastic gloves while handling chiles. Add chiles to blender with 1 cup of the remaining water. Blend to a smooth paste (about 2 minutes).

Add chile paste to dutch oven and add 1 cup of the remaining water, broth, thyme, bay leaf, pork, and any accumulated juices. Bring to a boil over high heat. Reduce heat, cover tightly, and simmer for 1 hour and 15 minutes.

Combine flour with remaining 2 tablespoons water and mix until smooth. Add to dutch oven with cumin and salt. Stir until well blended and simmer, uncovered, for 10 minutes more or until slightly thickened. Flavors improve and mellow if chili is refrigerated overnight or for at least 4 hours. Reheat over low heat.

Place chiles in a mixing bowl, cover with boiling water, and let stand for 20 minutes to rehydrate. When chiles are rehydrated, remove from water (discard water). Wear rubber or plastic gloves while handling chiles. Remove stems, seeds, and membranes and chop chiles. Whisk together orange juice and olive oil, add to chiles, and let stand for at least 15 minutes to blend flavors. At serving time, spoon mixture over individual bowls of chili and serve immediately.