In a small bowl, mix together 4 Tbsp. soy sauce, 2 Tbsp. honey, the oil, garlic, 1 tsp. ginger, and the red pepper flakes (optional).
Put the chicken in a large dish with sides, pour the marinade over it, and turn the chicken several times to coat it. Cover and refrigerate it for at least 30 minutes and up to 24 hours.
When you are ready to cook the chicken, preheat the grill or the broiler (with the rack about 4 inches from the heat), and coat a grilling tray or baking sheet with nonstick cooking spray or line it with foil.
Remove the chicken from the marinade and transfer it to the tray or pan, discarding the marinade. Grill or broil the chicken for 4 - 5 minutes per side until it is cooked through and the edges are browned.
While the chicken is cooking, in a medium bowl, whisk together ½ cup hot water, the peanut butter, lime juice, 1 tsp. soy sauce, 1 tsp. honey, and 1 tsp. ginger until it is smooth. Serve the chicken immediately with the sauce on the side for dipping, refrigerate for up to 3 days, or freeze for up to 3 months.