Preheat the oven to 250 degrees.
Combine the first 2 ingredients thoroughly in a small bowl to make the Seasoning Mix.
Melt the butter in an 8-inch skillet over high heat. When the butter starts to sizzle, add the onions, bell peppers, and 3 tablespoons of the Seasoning Mix. Cook, flipping and stirring the onions and peppers occasionally, until the onions are golden brown, about 6 minutes. Transfer to a bowl, and let cool.
Remove the giblets from the chicken and clean out the cavity. Stuff the cavity with the cooled vegetables and fold the skin flaps over the stuffing to keep it in.
Sprinkle 1 tablespoon of the seasoning mix all over the outside of the chicken, and rub it in well with your hands.
Place the chicken in a large baking pan and bake until tender, about 3 hours. Remove from the oven and set aside until the chicken is cool enough to handle.
Remove the stuffing from the chicken, and put the stuffing and any juices that have accumulated in the cavity of the chicken in the baking pan.
Cut the chicken in half lengthwise along the breastbone and backbone and carefully remove the bones, pulling out the breastbone first. The bones will come out easily if you take your time.
Place the baking pan over high heat and whisk the flour into the stuffing until it's completely absorbed. Whisk in the chicken stock and cook, whisking until thoroughly blended, about 1 to 2 minutes. Cook the gravy 2 minutes more, and remove from the heat. Makes 3 cups.
Serve the chicken with the gravy over rice or mashed potatoes.