Ensure the turkey breast is completely thawed (can take 1-3 days in the fridge). Do not thaw in the crockpot for food safety reasons. Remove packaging, discard gizzards, and throughly pat dry all over with paper towels.

Generously spray a 6-quart crockpot with nonstick spray.

Place cut celery, halved unpeeled onions, unpeeled garlic halves, and carrots in an even layer on the bottom of the crockpot. If it all doesn't fit in one layer, omit excess.

Mix all seasonings with olive oil in a bowl. Loosen the skin of the turkey with a large spoon and rub the mixture all over, especially under the skin.

Place the other halved unpeeled onion and 4 tablespoons of butter inside the turkey's cavity.

Place the turkey breast on top of the veggies, breast/skin side up. Cover and cook on low for 5-7 hours until the internal temperature reaches 160°F. (No liquid needed; turkey will produce plenty!) Avoid cooking on high; dries out turkey.

Optional Crisp: After cooking, transfer the turkey to a pan or casserole dish, drizzle with 1 tbsp oil, spray all over with cooking spray, and broil 1 foot from heat source for 4-8 minutes (watching very closely) until the skin crisps.

Cut the large breasts off center bone and slice the meat thinly against grain.

Strain the contents of the crockpot into a bowl, pressing veggies to extract flavor/liquid. Measure out 2 cups of this liquid (add chicken broth to reach this amount if necessary). In a pot, melt 4 tablespoons butter, then whisk in 4 tablespoons flour for 1 minute. Gradually add the strained liquid, while whisking constantly until nicely thickened. Season with salt, pepper, and any additional seasonings. Serve warm with the turkey.