In a small bowl, add the lemon zest, lemon juice, honey, olive oil, black pepper, red chili flakes, paprika, garlic powder, mustard powder and salt. 

Toss the chicken thighs until they are evenly coated with the mixture.

Preheat your oven to 400°F (200°C).

Bake the Chicken: Arrange the coated chicken thighs on a baking sheet lined with parchment paper or aluminum foil. Place the lemon slices on and around the chicken thighs. Bake in the preheated oven for 35-40 minutes, or until the internal temperature reaches 165°F (75°C) and the skin is golden and crispy.

Broil on high at the last 2 minutes of cooking to get a nice crispy skin and char.

Let it rest before serving. 

Preheat the Air Fryer: Preheat your air fryer to 375°F (190°C).

Arrange the coated chicken thighs in a single layer in the air fryer basket. Place the lemon slices on and around the chicken thighs. Cook for 18-22 minutes, flipping halfway through, until the internal temperature reaches 165°F (75°C) and the skin is crispy and golden.

Broil on high at the last 2 minutes of cooking to get a nice crispy skin and char. 

Let it rest before serving.