Place the vegetables in the bottom of a lightly greased crock pot to make a full layer.
Pat the turkey breast dry and set aside.
Melt the butter and mix in the seasonings. Baste each breast on both sides, then place in the crock pot on top of the vegetables.
Set crock pot to low and cook for 3.5-4 hours or when an instant read thermometer reaches 165F when inserted into the thickest part of the breast. Check for doneness around 3-3.5 hours.
Once cooked through, remove the turkey and allow to rest on a baking sheet for about 15-20 minutes before broiling the skin (reserve the juices from the crock pot for later).
While the turkey is resting, make your gravy by adding chicken stock and apple cider to a medium pot. Bring to a boil over medium to medium-high heat.
Keep a boil going, whisking as needed, until the mixture has reduced by about half (about 10 minutes).
Add in the all-purpose flour, and whisk until there are no lumps. Then, pour the mixture into the crock pot juices. Keep at a boil and whisk periodically until the desired thickness is reached (about 5-10 minutes).
Season with any salt and pepper as desired.
Position the oven rack to the middle section and preheat to broil. Allow the skin to crisp up to your preference (about 3-5 minutes).
It's important to use completely thawed turkey breast for this recipe. Allow it to thaw in the refrigerator.
We used two 1.5-pound turkey breasts, totaling 3 pounds. You can use two 1.5-pound breasts or a single 3-pound breast here depending on what you can find at the store. A single 3-pound breast may take up to 6 hours to cook as opposed to two 1.5-pound breasts. The cook time will also depend on the model and age of your slow cooker. The best way to check for doneness is with an instant-read thermometer inserted into the thickest portion of the breast. It's ready to go when it reaches 165F.