In a large stockpot, combine 2 quarts of the water with the kosher salt and sugar. Heat over medium heat, stirring until both fully dissolve (about 5 to 7 minutes).

Remove the pot from heat and add bay leaves, peppercorns, allspice berries, rosemary, thyme, orange quarters, lemon quarters, and smashed garlic. Let steep for about 10 minutes.

Cool the mixture to room temperature for about 30 minutes, then stir in the remaining 2 quarts of cold water and ice cubes.

Place the turkey in a brining bag, large stockpot, or clean cooler. Pour the cooled brine over the turkey, ensuring it is fully submerged.

Refrigerate or keep in a cooler packed with ice, maintaining a temperature below 40°F for 12 to 18 hours (do not brine longer than 24 hours).

After brining, remove the turkey from the brine and discard the brine and aromatics.

Rinse the turkey well under cold running water, then pat it dry with paper towels. If possible, let it air-dry uncovered in the refrigerator for 1 to 2 hours.

Roast the turkey using your preferred method, checking the internal temperature for 165°F.