Pour 2 quarts of cold water into a large pot or container and stir in 1/2 cup kosher salt until completely dissolved, about 2 minutes.

Add 1/4 cup granulated sugar and stir for 1 minute until fully dissolved.

Stir in the peppercorns, thyme, rosemary, bay leaves, smashed garlic, red pepper flakes, and lemon zest to build flavor.

Cool the brine to room temperature, then refrigerate it for at least 30 minutes until thoroughly chilled.

Submerge the chicken in the cold brine, ensuring it is completely covered; weight it down with a plate if necessary.

Refrigerate and brine the chicken for 8–24 hours, depending on desired flavor intensity.

Remove the chicken from the brine, discard the liquid, and rinse the bird under cold running water for 30 seconds to remove excess salt.

Pat the chicken thoroughly dry with paper towels, focusing on the skin for optimal browning.

Preheat the oven to 425°F (220°C). Place the chicken on a rack in a roasting pan and roast for about 1 hour 15 minutes, or until the thickest part of the thigh reaches 165°F (74°C).

Rest the chicken for 10 minutes before carving to allow juices to redistribute, then serve hot.