Remove the giblets from the bird and refrigerate. Chop optional onions and garlic cloves.

Add the two gallons of filtered water to the large stockpot or bucket. Mix in the sea salt and optional sugar until dissolved. Simmer optional onions, garlic, and bay leaves in a small amount of water for a couple of minutes to stimulate the release of flavors. Do not thoroughly cook them. Cool and stir into the brine water.

Place the turkey in the stockpot carefully and ensure that it is fully submerged in the brining liquid. Use a heavy plate or small tray to weigh the bird down and keep it fully submerged if necessary. Placing a small but weighty item into the crevice where the giblets were will also work to weigh the turkey down.

Cover and place the container in the refrigerator for at least 18 and up to 24 hours. Flip the turkey once or twice during that time.

After brining is complete, remove the turkey carefully, rinse well and place on a large platter. Discard the brine water. 

Pat the turkey dry with cotton towels. If you have time, let the turkey sit uncovered on a rack sitting on a baking sheet for 2-3 hours before roasting. This is because the skin has absorbed the brine as well as the meat. Drying it off before cooking will help it brown and get crispy like a non-brined turkey.

Making gravy from the drippings of a brined turkey can be very salty if you add additional salt during the gravy making process, so don't do this until you've tasted the gravy first!

If you will not be roasting the turkey within a few hours, place back into the refrigerator until you are ready to cook it.