Combine the salt, onion powder, paprika, Italian seasoning, garlic powder, and pepper in a small dish.
1 teaspoon kosher salt, ½ teaspoon onion powder, ½ teaspoon ground paprika, ½ teaspoon Italian seasoning, ¼ teaspoon garlic powder, ¼ teaspoon ground black pepper
Place the chicken breasts in the slow cooker. Rub the seasonings and olive oil over the chicken breasts.