Rinse the chicken thighs under cold water and pat them dry with paper towels. Season with salt and black pepper on both sides.
In a large skillet, heat olive oil over medium-high heat. Sear the chicken thighs skin side down for about 5 minutes until golden brown, then flip and cook for an additional 3 minutes. Transfer to the crockpot.
Chop the vegetables: peel and slice the carrots, dice the potatoes, chop the onion, and mince the garlic.
Place the sliced carrots, diced potatoes, chopped onion, and minced garlic around the chicken in the crockpot. Sprinkle dried thyme and rosemary over the top, and add the bay leaf.
Pour the chicken broth over the chicken and vegetables, ensuring it covers the ingredients well.
Cover the crockpot and cook on low for 6-8 hours or on high for 4-5 hours. Add frozen peas in the last 30 minutes of cooking.
If a thicker sauce is desired, mix cornstarch and water to create a slurry, stir it into the crockpot, and let it cook for an additional 10-15 minutes. Remove the bay leaf before serving.