Line extra-large stockpot with heavy large plastic bag (about 30-gallon capacity). Before I had one, a Home Depot bucket worked just dandy. Rinse turkey; place in plastic bag. Stir 8 quarts water, 2 cups coarse salt and 1½ cups honey in large pot until salt and honey dissolve. Add 2 bunches fresh thyme, peeled garlic cloves and black pepper. Pour brine over turkey. Gather plastic bag tightly around turkey so that bird is covered with brine; seal plastic bag. Refrigerate pot with turkey in brine at least 12 hours and up to 18 hours.
Position rack in bottom third of oven and preheat to 350°F. Drain turkey well; discard brine. Pat turkey dry inside and out. Squeeze juice from lemon halves into main cavity. Add lemon rinds and remaining 1 bunch fresh thyme to main cavity. Tuck wings under turkey; tie legs together loosely to hold shape. Place turkey on rack set in large roasting pan. Rub turkey all over with 3 tablespoons olive oil.
Roast turkey 1 hour. Baste turkey with 1 cup chicken broth. Continue to roast until turkey is deep brown and thermometer inserted into thickest part of thigh registers 180°F, basting with 1 cup chicken broth every 30 minutes and covering loosely with cheese cloth if turkey is browning too quickly, about 2½ hours longer. Transfer turkey to platter. Tent turkey loosely with foil and let stand 30 minutes. Pour pan juices into large glass measuring cup. Spoon off fat; reserve juices.
For gravy:
While turkey cooks, place reserved turkey neck, into large saucepan. Add 6 cups water, 3½ cups chicken broth, carrots, onion, celery and bay leaf. Simmer over medium heat until turkey stock is reduced to 3 cups, about 2 hours. Strain turkey stock into bowl; reserve turkey neck to pull meat off neck for gravy.
Melt 5 tablespoons butter in heavy large saucepan over medium heat. Add 5 tablespoons all purpose flour and whisk 2 minutes. Gradually whisk in turkey stock, cream and up to 1 cup reserved turkey pan juices (juices are salty, so add according to taste). Simmer gravy until thickened to desired consistency, whisking occasionally, about 5 minutes. Add chopped turkey neck meat; season to taste with pepper.
Serve turkey with gravy.
Recipe by Sugar and Spice at https://kathleenssugarandspice.com/2013/11/25/honey-brined-turkey-with-gravy/