Heat the olive oil in a skillet over medium heat. Add the diced onion and sauté for 3-4 minutes until softened and translucent.

Stir in the minced garlic and cook for another 1-2 minutes until fragrant. Transfer the cooked onion and garlic mixture to the bottom of the slow cooker.

Place the chicken breasts on top of the onion and garlic mixture. Sprinkle the dried thyme, dried rosemary, lemon zest, salt, and black pepper evenly over the chicken.

Add the uncooked rice around the chicken in the slow cooker. Pour the chicken broth over the rice and chicken, ensuring the rice is completely submerged in the liquid.

Drizzle the fresh lemon juice over everything in the slow cooker. Cover with the lid and cook on low for 3-4 hours or on high for 1.5-2 hours, until the chicken is fully cooked and the rice is tender.

Once cooking is complete, remove the chicken breasts from the slow cooker and set aside. Stir the frozen peas into the rice and broth mixture, allowing them to warm through.

Shred or slice the chicken breasts and return them to the slow cooker. Gently stir to combine the chicken, rice, peas, and broth.

Taste and adjust seasoning with additional salt or pepper if needed. Sprinkle the chopped fresh parsley over the top just before serving.