Preheat your oven to 425°F (220°C). This high temperature will help achieve a crispy skin.
Place the whole chicken on a cutting board, breast-side down. Using a sharp knife, carefully split the chicken down the back.
In a bowl, whisk together the olive oil, yellow mustard, honey, crushed garlic, dried rosemary, crushed red pepper flakes, salt, pepper, and the zest of 1/4 of the lemon.
Turn the chicken over so it’s breast-side up. Use a basting brush to generously coat the chicken with the marinade.
Cut the lemon in half and squeeze the juice over the chicken, then place the squeezed halves inside the cavity of the chicken along with the whole cloves of garlic.
Transfer the chicken to the preheated oven. Roast for about 45-60 minutes, or until the internal temperature reaches 165°F (75°C).
Once done, remove the chicken from the oven and let it rest for about 10-15 minutes.
Garnish with fresh parsley and lemon wedges. Carve the chicken and serve with your favorite sides.