Prepare the Slow Cooker: Start by spraying the inside of your slow cooker with a bit of non-stick cooking spray for easy cleanup.
Layer Ingredients: Place the diced onion and minced garlic at the bottom of the slow cooker. Next, layer the chicken breasts on top.
Season and Add Rice: Sprinkle the chicken with thyme, rosemary, paprika, salt, and pepper. Then, add the rice evenly over the chicken.
Add Liquid: Pour the chicken broth on top of everything, ensuring the rice is submerged. Squeeze the lemon juice over the mixture and then add the lemon zest for extra flavor.
Cook: Cover the slow cooker and cook on low for 6-7 hours or on high for 3-4 hours, until the chicken is cooked through and tender, and the rice has absorbed the liquid.
Optional Add-in: During the last 30 minutes of cooking, add the frozen peas to the slow cooker if using, mixing gently to combine.
Finish and Serve: Once cooked, shred the chicken directly in the slow cooker using two forks. Stir everything together to combine flavors.
Garnish: Serve the chicken and rice in bowls, garnished with freshly chopped parsley for a burst of color.