Crisp-Skinned Butterflied Roast Turkey With Gravy

Chicken or turkey broth, low-sodium homemade or store-bought

roughly chopped qt 4 stalks celery

Bay leaves

Carrots, peeled and roughly chopped (about 1 quart), large

Onions, roughly chopped (about 1 1/2 quarts), large

Thyme, sprigs

Flour

Kosher salt and freshly ground black pepper

Vegetable oil

Butter