Arrange chicken breasts in a large slow cooker. Season generously with salt and pepper and pour the chicken broth into the bottom. Cover and cook on LOW for 4 to 6 hours, or until chicken is fall-apart tender.

Remove chicken from slow cooker to cutting board, cut into chunks, and shred. Drain the liquid from the slow cooker and wipe it out. Return the shredded chicken to the empty slow cooker.

In a medium bowl, whisk together coconut milk, peanut butter, garlic, honey, soy sauce, lime juice, rice wine vinegar, fish sauce, and red pepper flakes until smooth. Pour over chicken in slow cooker and stir to coat.

Cover and cook on LOW for 45 minutes to 1 hour longer, stirring halfway through, or until the sauce is thickened and everything is heated through.

Serve chicken and sauce over cooked white or brown rice, cooked rice noodles, or stuffed inside large lettuce leaves, as wraps. Garnish with chopped peanuts, fresh cilantro, and additional red pepper flakes, if desired.