Arrange celery, carrots, onion, potatoes, four cloves of garlic, four springs of rosemary, and thyme sprigs in an 8-quart slow cooker bowl, creating a nest for the chicken with the vegetables.

In a small bowl, combine salt, paprika, black pepper, dried thyme, Italian seasoning, and olive oil to make a paste.

Remove the giblets and neck from the chicken. Pat the outside and inside of the chicken dry with paper towels.

Spread the paste evenly over the chicken skin.

Stuff the chicken with the quartered lemon, four garlic cloves, and six rosemary sprigs.

Place the chicken breast side up on the vegetables.

Tie the chicken legs.

Cover and cook on the “High” setting for 4 to 5 hours or “Low” setting for 6 to 8 hours, or until the breasts reach an internal temperature of 160 to 165ºF and the thighs reach 170ºF.

Line a baking dish or tray with foil.

Brush the chicken with olive oil and broil 10 inches away from the top of the oven until the skin is browned and crispy, about 5 minutes.

To brown the vegetables, transfer them to a foil-lined baking dish and broil them 10 inches away from the top of the oven for 8 - 10 minutes.

Let the chicken rest for 15 minutes before carving.

Add vegetables to a platter, and place carved chicken on top.

Transfer chicken drippings to a fat separator and set aside the dripping.

Melt two tablespoons of unsalted butter in a medium saucepan over medium heat and then whisk in two tablespoons of flour. Once a pale roux is formed, gradually whisk in 1 cup of the chicken drippings, stirring continuously until thickened, about 2 minutes. Add more chicken drippings for a thinner sauce. Season with salt and pepper to taste.