Prep the Turkey: Remove giblets and neck from the turkey. Rinse the turkey under cold water and pat it dry with paper towels.
Season the Turkey: Rub the turkey inside and out with kosher salt, black pepper, and melted butter or olive oil.
Prepare the Vegetables: Place diced onions, carrots, celery, and smashed garlic at the bottom of the slow cooker to form a flavorful base.
Add Herbs and Turkey: Lay fresh thyme sprigs over the vegetables, then place the turkey breast-side up in the slow cooker.
Cook the Turkey: Cover the slow cooker and cook on low for 6-8 hours, or until the internal temperature reaches 165°F at the thickest part of the breast.
Rest the Turkey: Allow the turkey to rest for 20-30 minutes after cooking to lock in the juices.
Serve: Carve the turkey and serve with the vegetables. Enjoy!