Preheat the oven to 450°F. In a shallow braising pan or a large ovenproof skillet, toss together the potatoes, leeks, olive oil, salt, and red pepper flakes. Spread evenly over the bottom of the pan.

In a small bowl, mix together the chopped thyme, rosemary, lemon zest, salt, and olive oil.

Pat the chicken dry with a paper towel. Gently slide your fingers under the skin along the breast, being careful not to tear the skin, and rub 1/3 of the seasoning mixture under the skin. Rub the remaining seasoning all over the outside and inside of the bird. Stuff the cavity with the herb sprigs, lemon half, and garlic. Tie the legs together, crossing the ankles, using butcher’s twine.

Place the dressed bird on top of the vegetables and place the pan in the oven. Roast for 55 to 60 minutes, adding the chicken broth to the bottom of the pan for the last 15 minutes of cooking. An instant-read thermometer should read 155°F in the thickest part of the thigh. Allow the chicken to rest for 15 minutes before carving and serving with the vegetables and pan sauce.