Dry the turkey breast thoroughly with paper towels, and if it has skin, gently lift it to season beneath.
Combine melted butter, olive oil, minced garlic, salt, pepper, garlic powder, onion powder, paprika, thyme, rosemary, sage, and lemon zest in a bowl.
Massage the seasoning mixture generously all over the turkey, making sure to cover underneath the skin as well.
Arrange sliced onion, chopped celery, chopped carrot, and extra garlic at the bottom of your crockpot.
Pour the chicken or turkey broth along with Worcestershire sauce over the vegetables.
Set the turkey breast on top of the veggies, cover the crockpot, and cook on low heat for 5 to 6 hours depending on the turkey’s size, until the internal temperature hits 165°F.
If you prefer crispy skin, place the cooked turkey under the broiler for 4–5 minutes after slow cooking.
Allow the turkey to rest for 10 to 15 minutes before carving and serving.