Preheat oven to 400˚F.
Pat chicken thighs dry with paper towel. Sprinkle both sides of thighs with 1 1/2 teaspoons salt and 1/2 teaspoon pepper.
Place skillet over medium-high heat. Add oil and swirl to even coat skillet. Add thighs, skin-side down, and sear for 5 to 6 minutes or until skin is brown and has crisped. Flip each thigh and continue to sear for an additional 3 to 4 minutes.
Remove thighs from skillet and transfer to a plate.
Toss potatoes, 1 1/2 teaspoons thyme leaves, garlic, oil, lemon juice, and remaining salt and pepper together in a bowl until potatoes are evenly coated.
Pour potatoes into skillet in an even layer.
Top potatoes with chicken thighs, skin-side up, and add sprigs of thyme.
Transfer skillet to oven and bake for 25 to 30 minutes or until thighs have cooked through (juices should run clear when chicken is cut into and internal temp is 165˚F) and potatoes are fork tender.
Remove chicken and potatoes from oven and allow chicken to rest, about 5 minutes. Top with remaining thyme, lemon zest and sea salt flakes (optional). Serve.