1. Combine 6 tablespoons flour with 1/2 teaspoon each salt and pepper in a shallow bowl. Dredge chicken thighs in the mixture to coat completely; transfer to a plate.
2. Heat 2 teaspoons oil in a large skillet over medium-high heat. Add half the chicken and cook until well browned, 2 to 4 minutes per side; transfer to a 5- to 6-quart slow cooker. Reduce heat to medium and repeat with the remaining 2 teaspoons oil and chicken thighs. Arrange the chicken in an even layer in the slow cooker.
3. Add bacon to the pan and cook, stirring often, for 2 minutes. Sprinkle the remaining 1/2 cup flour over the bacon and cook, stirring constantly, for 2 minutes more. Add stout and use a wooden spoon to scrape up any browned bits from the bottom of the pan. Pour the mixture over the chicken. Add carrots, mushrooms, onion, garlic and thyme, spreading in an even layer over the chicken. Pour broth over the top.
4. Cover and cook until the chicken is falling-apart tender, 4 hours on High or 7 to 8 hours on Low.
5. Stir in peas, cover and cook until the peas are heated through, 5 to 10 minutes more. Season with the remaining 1/2 teaspoon salt and pepper.
To Make Ahead: Trim chicken, chop bacon; prep onion and garlic; defrost peas. Refrigerate in separate containers. Equipment: 5- to 6-quart slow cooker.