1. Prepare Chicken and Season in Slow Cooker:
- Place the boneless, skinless chicken breasts in the bottom of your slow cooker insert.
- Season the chicken breasts directly in the slow cooker with salt, pepper, dried oregano, dried basil, and red pepper flakes (if using).
2. Add Remaining Ingredients:
- Add the undrained canned diced tomatoes over and around the chicken.
- Scatter the pitted and halved Kalamata olives, sliced red onion, and minced garlic on top of the chicken and tomatoes.
3. Slow Cook:
- Place the lid securely on the slow cooker.
- Cook on the LOW setting for 6-7 hours OR on the HIGH setting for 3-4 hours. The chicken should be cooked through, very tender, and easily shredded with a fork.
4. Serve:
- Once cooked, you can serve the chicken breasts whole or shred them slightly with two forks directly in the slow cooker sauce.
- Serve the chicken and the surrounding tomato-olive sauce mixture hot over cooked couscous or quinoa.
- Garnish generously with fresh chopped parsley just before serving.