Preheat oven to 400°F (200°C). Cut the top quarter off one head of garlic to expose the cloves. Drizzle with 1 tbsp olive oil, wrap in foil, and roast for 30 minutes until soft.

Once cooled, squeeze the roasted garlic cloves into a small bowl and mash into a paste. Add softened butter, chopped thyme, chopped rosemary, lemon zest, salt, and pepper. Mix until well combined.

Remove giblets from the chicken and pat it completely dry with paper towels. Gently separate the skin from the breast and thighs, being careful not to tear it.

Rub the garlic herb butter all over the meat underneath the skin. Rub the outside of the chicken with the remaining 1 tbsp of olive oil and season generously with salt and pepper.

Stuff the chicken cavity with the squeezed garlic head, the halved lemon, and the sprigs of thyme and rosemary. Truss the legs together with kitchen twine.

Place the chicken, breast-side up, on a rack in a roasting pan. Roast for 1 hour 15 minutes to 1 hour 30 minutes, or until an instant-read thermometer inserted into the thickest part of the thigh registers 165°F (74°C).

Transfer the chicken to a cutting board and let it rest for 15-20 minutes before carving. This is crucial for a juicy chicken. Garnish with fresh herbs and serve.