For turkey: Using your fingers, gently loosen skin from turkey breast. In a small bowl, stir together thyme, onion powder, salt and pepper. Rub mixture under skin.
In a large skillet, heat canola oil over medium-high heat. Cook turkey until browned on both sides, approximately 2 minutes per side. Remove from heat.
Place turkey in a 6-quart slow cooker. Add broth to skillet, stirring to loosen browned bits. Add broth mixture to slow cooker. Cover and cook on low until tender, 5 to 6 hours.
Remove turkey from slow cooker. Cut into slices; place on a serving platter, cover with aluminum foil. Strain turkey drippings; reserve 2 cups.
For gravy: In a medium saucepan, add flour and pepper. Whisk in 2 cups reserved turkey drippings. Bring to a boil over medium-high heat, whisking constantly. Reduce heat to medium-low; simmer until thickened, approximately 2 minutes. Add salt to taste. Serve gravy with turkey. Decorate platter with thyme, if desired.