Add carrots, onions, and celery to slow cooker. Toss with flour and top with chicken thighs. Season with salt, pepper, and lemon zest. Add chicken broth, then cover and cook until the vegetables are tender and the chicken is cooked; 5-6 hours on low or 3-4 hours on high.

Make biscuits 30 minutes before you plan to serve. Just before serving, stir in heavy cream, lemon juice, and peas. Cook until warmed through. Season to taste with salt and pepper.

Split biscuits in half in shallow bowls, topping with the chicken and vegetables. Garnish with parsley.