Heat olive oil in a large skillet over medium-high heat. Pat chicken thighs dry, then season with salt and pepper on both sides. Sear thighs 3-4 minutes per side until golden brown, working in batches to avoid overcrowding the pan.

Transfer seared chicken to your slow cooker, setting aside the skillet. The browned bits create flavor foundation that the slow cooker chicken will absorb beautifully during cooking. Add diced onion, minced garlic, and sliced mushrooms directly over the chicken.

Pour chicken broth into the skillet and scrape up all browned bits using a wooden spoon. Stir in tomato paste, thyme, rosemary, paprika, and bay leaves. Pour this fragrant mixture over the chicken thighs recipe components.

Cover and cook on LOW setting for 6 hours until cozy slow cooker chicken thighs are fall-apart tender and vegetables are completely soft. The extended cooking time transforms tough connective tissue into silky gelatin.

Add sliced carrots and chopped celery directly to the slow cooker during the final 45 minutes of cooking. This timing prevents vegetables from becoming mushy while ensuring they absorb flavors fully.

Mix cornstarch with water to create a slurry, then stir into the simmering broth. Increase heat to HIGH setting and cook 15 minutes until sauce thickens into silky consistency coating the chicken.

Remove bay leaves before serving. Taste and adjust seasonings as needed—add more salt, pepper, or herbs based on preference.