Dice the chicken into 1-inch pieces and season with salt and pepper.
In a skillet, heat olive oil and sear the chicken on all sides (about 4–5 minutes). Transfer to the slow cooker.
Add flour, thyme, rosemary, and salt to the slow cooker. Toss the chicken until coated.
Add the garlic, onion, carrots, and potatoes. Stir to combine, then pour in the chicken broth and add the bay leaf.
Cover and cook on low for 7–8 hours (or high for 3–4 hours).
When done, stir in the frozen peas and milk. Cook on high for another 10–15 minutes until the peas are heated through.
Adjust the stew’s thickness by adding flour or broth. Taste and season with additional salt and pepper before serving.