Prepare the turkey: Pat the turkey breast dry with a paper towel.
Season well: Mix garlic powder, onion powder, paprika, salt, and pepper with olive oil, then rub it all over the turkey.
Layer the crockpot: Place onion halves, garlic, and thyme at the bottom, then set the turkey breast on top.
Slow cook: Cover and cook on low for 6 hours or until the internal temperature reaches 75°C (165°F).
Rest the turkey: Remove and let it rest for 10 minutes before slicing.
Make the gravy: In a saucepan, melt butter, whisk in flour, and slowly add cooking juices, stirring until thickened.
Slice and serve: Serve warm with the homemade gravy and your favorite sides.