Brown the meat: In a large saute pan heat 1 tablespoon of the oil over medium heat. When the oil begins to smoke lightly, add the beef and season with salt. Cook over medium heat, stirring with a wooden spoon, until the meat browns, about 5 minutes. Transfer beef to a large mixing bowl.
Brown the vegetables: In the same pan, stir in the onions and the remaining oil. Add the garlic, chiles, bell pepper, tomato paste, and a generous pinch of salt. Cook until the vegetables start to brown, about 5 minutes.
Cook the chili: While the vegetables are cooking, to the slow cooker add the tomatoes, chili powder, bay leaf, cumin, allspice, red pepper flakes, and 2 cups of water; stir to combine. Add the vegetables to the bowl of meat and stir to combine, then add to the slow cooker. Stir in the vinegar. Cover and set the cooker to low; cook for about 8 hours. Check after a couple of hours. Stir and taste for seasoning. Thirty minutes or so before serving, turn the slow cooker to high and stir in the black beans and cook for an additional 30 minutes.
Serve: Allow it to "rest" for about 15 minutes before serving. Stir in the scallions. Taste for seasoning. Serve with any or all of the following: cheddar, sour cream, avocado, scallions, lime wedges, and tortilla chips.