Place the chicken thighs, sliced mushrooms, chopped onion, sliced carrots, sliced celery, and minced garlic into the slow cooker.
In a small bowl, whisk the flour with 1/2 cup of the chicken broth until smooth. Pour this mixture into the slow cooker along with the red wine, remaining broth, dried thyme, and a pinch of salt and pepper. Stir gently to combine.
Cover and cook on low for 6 hours, until the chicken is tender and the vegetables are soft.
Remove the chicken thighs, shred them with two forks, and return the meat to the slow cooker. Stir in the frozen peas and let everything sit for 10 minutes so the peas warm through and the gravy thickens slightly.
Spoon the filling into bowls and top each serving with a baked biscuit.