In a small bowl, stir butter, poultry seasoning, garlic herb sauce mix, and crushed garlic together with a fork until combined. Cover and refrigerate for 15 minutes, or until firm. Stir together flour and 1/2 cup of chicken broth; set aside.
Heat oven to 450 degrees F. Place celery, carrots and half of the onions in the bottom of a roasting pan. Add the remaining 3-1/2 cups chicken broth to pan and set aside.
Rinse turkey and pat dry. Loosen skin with your hands around the entire bird.
Remove butter from the refrigerator and place small pieces of it under the skin of the turkey. Sprinkle with salt and pepper. Stuff the inside of the turkey with remaining onions, fresh poultry herbs and lemon slices.
Place turkey, breast side up, on a rack over the vegetables in the roasting pan. Place in oven and reduce heat to 325 degrees F. Roast for 1 hour, then baste with juices every 20 minutes for 2 hours or until an instant read thermomter inserted in the thigh or thickest part of the breast registers 160 degrees F.
Remove turkey from roasting pan and cover with foil and set aside. Strain contents of roasting pan into a fat separator. Pour liquid into a saucepan and discard fat. Bring liquid to a boil over medium-high heat. Pour flour mixture and Worcestershire sauce into liquid while whisking. Boil for 3 minutes or until thickened.
After turkey has rested for 20 minutes, carve. Serve with gravy.