Pat the chicken thighs dry with paper towels to help keep the sauce from getting watered down.

In a small bowl, whisk together the dry onion soup mix, condensed cream of mushroom soup, and 1/2 cup low-sodium chicken broth or water until mostly smooth and combined enough to pour.

Arrange the raw chicken thighs in one snug layer in the bottom of a round slow cooker, skin side up, allowing only slight overlap and avoiding deep layers.

Pour the soup mixture evenly over and around the chicken thighs, letting it run down between them, and do not stir.

Cover the slow cooker and cook on LOW for 5 to 6 hours or on HIGH for 3 to 3 1/2 hours, until the chicken is very tender and reaches at least 165°F in the thickest part without touching the bone.

Carefully lift the cooked thighs out with tongs and transfer them to a serving platter, then skim excess fat from the sauce if desired.

Stir the remaining cooking juices in the slow cooker until smooth, then spoon the gravy generously over the chicken and serve with mashed potatoes, buttered egg noodles, white rice, vegetables, or bread.

For crisper skin, transfer the cooked thighs skin side up to a foil-lined sheet pan and broil for 2 to 4 minutes, watching closely, until the skin browns and bubbles, then serve with the slow cooker gravy.