1. Prepare Your Vegetables: Start by chopping your onion, peeling and chopping the carrots, and slicing the celery stalks. Aim for roughly similar-sized pieces so they cook evenly.

2. Add Chicken and Vegetables to Slow Cooker: Place the boneless, skinless chicken thighs at the bottom of your slow cooker. Then, evenly distribute the chopped onion, carrots, and celery over the chicken.

3. Combine Wet Ingredients and Seasonings: In a medium bowl, whisk together the crushed tomatoes, diced tomatoes (with their liquid), low-sodium chicken broth, and tomato paste. Add the minced garlic, dried oregano, dried thyme, and black pepper. Stir until all ingredients are well combined.

4. Pour Sauce Over Ingredients: Carefully pour the tomato mixture over the chicken and vegetables in the slow cooker. Ensure everything is mostly submerged in the liquid.

5. Cook Until Tender: Cover your slow cooker and cook on the LOW setting for 7-8 hours, or on the HIGH setting for 4-6 hours. The stew is ready when the chicken is incredibly tender and easily shreds with a fork, and the vegetables are soft.

6. Shred Chicken and Add Peas: Once cooked, carefully remove the chicken thighs from the slow cooker and shred them using two forks. Return the shredded chicken to the slow cooker. Stir in the frozen peas and cook for an additional 10-15 minutes, or until the peas are heated through.

7. Taste and Adjust Seasoning: Give the stew a taste and add salt as needed. Remember, you can always add more salt, but you can’t take it away.

8. Garnish and Serve: Ladle the warm stew into bowls. If desired, garnish with fresh chopped parsley for a burst of color and fresh flavor.