Cook bacon over medium heat until crisp, about 8 minutes. Add bbacon to the crockpot. Reserve the bacon fat separately. You should have at least 2 T. If not, use vegetable oil for the missing fat.
Dry chicken with paper towels. Season with salt and pepper. Add 2 t. bacon fat to the skillet. Heat over medium-high heat until just smoking. Brown half of the chicken on both sides, about 10 minutes. Put in the crockpot. (Remove the browned skin if using thighs.) Return the skillet to medium high heat and repeat with 2 more teaspoons of fat and the rest of the chicken. Discard any fat left in the skillet.
Add the remaining 2 t. fat to empty skillet. Heat over medium heat until shimmering. Add cremini's, red onion and 1/4 teaspoons salt. Cook until mushroom are brown, 10-15 minutes. Stir in the garlic. Cook for 15 seconds. Stir in wine and tomato paste, scraping up any browned bits. Simmer until the wine has reduced by half, about 5 minutes. Put in crockpot.
Add tomatoes, 1.5 cups broth, porcini's, thyme, bay leaves and red pepper flakes to crockpot. Cover and cook on low until chicken is tender, about 4 hours.
Transfer chicken to large serving dish. Tent loosely with foil.
Discard bay leaves. Set the crockpot to high. Whisk flour with remaining 1/2 cup broth until smooth. Stir into crockpot. Cover and continue to cook until sauce is thickened and no longer tastes of flour, 15 to 30 minutes longer.
Stir in parsley. Season with salt and pepper to taste. Spoon vegetables and some of the sauce over the chicken. Serve, passing the remaining sauce separately.