In a large stockpot, combine the kosher salt, brown sugar, and 1 gallon of water.
Heat over medium heat, stirring until the salt and sugar have completely dissolved.
Remove from heat and add the black peppercorns, allspice berries, bay leaves, thyme, rosemary, crushed garlic, and lemon zest.
Allow the brine to cool to room temperature. You can speed up cooling by adding ice to the brine (just ensure it stays diluted).
Once cooled, submerge the turkey in the brine. If using a cooler, consider layering ice on top to keep the turkey cold.
Brine the turkey for 12 to 24 hours, depending on your taste preference and time available.
After brining, rinse the turkey under cold water to remove excess salt. Pat the turkey dry with paper towels before cooking.