Slice the roast into small cubes. Dry off the cubes with paper towels. In a large Dutch oven, sear them in bacon grease. Lower the heat, stir in flour, cumin, chili powder, garlic, oregano, tomato paste and onions. Cover with water or beef stock. Stir the pot until well incorporated. Bring the liquids to a boil, cut the heat to a slow simmer, cover and braise for 1 1/2 - 2 hours. Stir the pot - on occasion. Season to taste with salt - near the end of the cooking time. Garnish with lime wedges.
Experiment with a variety of dry, mild and hot chiles to achieve the perfect blend of color and heat. (From earthy to hot peppers - Ancho, Mulatto, California, New Mexican, Guajillo, cascabel, chile de arbol and chiltepin.)
An alternative means of thickening chili is to omit the flour in the recipe, and - about 5 minutes before serving, thicken it with a slurry consisting of Masa Harina dissolved in water.