Add the onion, carrots and celery and broth to the crockpot. Turn on low.
Mix all of the rub ingredients together in a small bowl.
Pat the turkey breast dry with paper towels. Rub smashed garlic on the skin. Add spice rub to turkey. Leftover spices put on top of vegetables.
Add garlic and lemon to the inner cavity of the breast. Place the breast on top of the veggies.
Cook on low for 3 1/2 to 5 hours, depending on the size of the breast. It should have an internal temperature of at least 160 degrees F.
Remove the turkey breast using turkey lifters and place in a roasting pan or baking dish. Place in the oven on the broil setting to crisp up the skin, for about 3 to 4 minutes, watching carefully so it won’t burn.
Make the Gravy
Strain the broth from the slow cooker (mine made about 1 1/3 cups)
Add 3 tablespoons of butter to a sauce pan and melt. Add flour and mix well, allowing the flour to cook for 3 to 4 minutes.
Slowly add the strained broth and mix, until desired consistency. Allow to simmer and thicken. Add water if needed to thin out the gravy (about 2 to 3 tablespoons).
Add dried thyme and salt and pepper to taste. Serve with the turkey breast.