Whisk together the olive oil, Dijon, lemon zest and juice, garlic, hot honey, salt, pepper, red pepper flakes, and thyme. Reserve about 1/4 cup of the marinade then add the rest to a ziplock bag or tupperware with the chicken. Marinate for 30 minutes to 24 hours.
Preheat a grill to medium-high heat. Grill the chicken until cooked through and lightly charred, about 4 to 6 minutes per side depending on thickness.
While the chicken cooks, lightly toss the peaches with the remaining marinade and grill until caramelized and grill marks form, about 4 to 5 minutes, flipping halfway.
Transfer everything to a platter and finish with fresh thyme, flaky salt, and a generous drizzle of hot honey.
