In a large, heavy-duty pot, add the vegetable broth, sea salt, rosemary, sage, and thyme. Bring to a boil, stirring frequently, until salt is dissolved. Remove from heat and let it cool to room temperature.
When the broth mixture has come to room temperature, pour it into a large bucket (5 gallons, or a bucket large enough to keep the turkey fully submerged). Pour in the ice water. NOTE: I did not have a brining bucket so I made everything right in the pot I boiled the broth in.
Remove the giblets (heart, neck, liver, heart) of your turkey and place it breast-side down into the brine. Be sure the cavity gets filled and the turkey is completely submerged. (If the turkey is floating, keep it down with a zipped bag full of ice.)
Cover the bucket and place it in the refrigerator for 12-24 hours.
Carefully remove the turkey from the brine, rinse it with cold water, and pat dry with paper towels. Discard the remaining brine.
Cook the turkey following your desired recipe. Reserve the drippings for gravy. (Please note: A brined turkey tends to cook more quickly, so begin checking the internal temperature of the turkey about an hour before the end of the original cooking time.)