Place chicken breasts between 2 sheets of plastic wrap. Flatten to ¼” thickness. Season with a pinch each salt, pepper, and garlic powder.
Fold cheese so it is about ½” narrower than ham. Place cheese on ham and fold in each of the long sides and then roll from one short end, burrito-style. This will help prevent the cheese from running out during the cooking process. Place one ham roll on a narrow end of each piece chicken and roll into a bundle.
Wrap a piece of bacon lengthwise around each chicken bundle and secure with a toothpick. Ensure the bacon tightly covers the ends of the bundle as it will also help prevent leaky cheese. Place the bundles into slow cooker.
Combine ½ cup water, bouillon and wine. Pour over chicken. Cover and cook 5-6 hours on LOW.
Just before serving, remove chicken from slow cooker. If needed, strain cooking liquid and return to slow cooker. Switch heat to HIGH. Combine cornstarch with remaining ½ cup water. Stir ½ cup of slow cooker liquid into the cornstarch mixture to temper and then add that back to slow cooker. Stir well until sauce thickens.