In a large pot, combine the kosher salt, brown sugar, black peppercorns, garlic, rosemary, and thyme.
Add 2 liters of water to the pot and heat over medium heat, stirring until the salt and sugar dissolve completely.
Remove the pot from heat and let the brine cool to room temperature.
Once cooled, add additional cold water or ice to ensure the brine is fully chilled before using.
Place the turkey in a large container or a cooler. Pour the brine over the turkey until completely submerged, adding more water if necessary to cover.
Seal the container or cooler and refrigerate for at least 12 hours, ideally 24 hours for best results.
After brining, remove the turkey from the brine and pat dry with paper towels. Discard the brine.
Proceed to cook the turkey according to your preferred method.