1. Prepare the Vegetables: Wash and quarter the small potatoes. Peel and cut the carrots into uniform 1-inch pieces. Chop the onion. Place all the prepared vegetables into the bottom of your slow cooker.

2. Season the Chicken: Pat the boneless, skinless chicken thighs or breasts dry with paper towels. In a small bowl, combine the olive oil, Italian seasoning, garlic powder, salt, and black pepper. Rub this mixture all over the chicken pieces, ensuring they are well coated.

3. Layer the Ingredients: Place the seasoned chicken pieces on top of the vegetables in the slow cooker. Distribute them evenly so they cook consistently.

4. Add Liquids: Pour the can of undrained diced tomatoes over the chicken and vegetables. Then, carefully pour the chicken broth around the ingredients, ensuring it reaches the bottom of the pot. The liquid is crucial for creating a moist and flavorful environment for slow cooking.

5. Set and Cook: Secure the lid on your slow cooker. Cook on the LOW setting for 6-8 hours, or on the HIGH setting for 3-4 hours. The chicken should be fork-tender and the potatoes easily pierced with a fork when done. Avoid lifting the lid too often, as this releases heat and extends the cooking time.

6. Serve and Garnish: Once cooked, use a slotted spoon to transfer the chicken and vegetables to serving plates. The chicken should shred easily. Ladle some of the flavorful cooking liquid over the top. Garnish with fresh chopped parsley, if desired, for a pop of color and freshness.