In a small bowl, combine paprika, thyme, poultry seasoning, onion powder, 1 1/4 teaspoons salt and 3/4 teaspoon pepper.
Place onion and celery into a 6-qt slow cooker; add chicken stock and wine.
Using your fingers, carefully loosen the skin from the breast meat, spreading 4 tablespoons butter under the skin. Secure skin over the butter with wooden picks; brush skin with 1 tablespoon melted butter and season with paprika mixture.
Place turkey, breast side up, on top of the vegetables. Cover and cook on low heat for 3-4 hours, reaching an internal temperature of 165 degrees F. Remove turkey from the slow cooker; let rest 10-15 minutes.
Strain slow cooker drippings through a fine-mesh sieve; discard solids.
Melt remaining 3 tablespoons butter in a medium saucepan over medium heat. Whisk in flour until lightly browned, about 1 minute.
Gradually whisk in pan drippings. Bring to a boil; reduce heat and simmer, whisking constantly, until thickened, about 5-10 minutes.