A method of forming a cast component and a method of forming a casting mold is generally provided. The method is performed by plugging or covering an opening in a ceramic core-shell mold. The ceramic core-shell mold includes at least a first core portion, a first shell portion, and at least one first cavity between the core portion and the first shell portion. The core-shell mold may be manufactured using an additive manufacturing process. At least a portion of the ceramic core-shell mold and the plug or cover is coated with a second ceramic material.