Flow path assemblies and methods for forming such flow path assemblies for gas turbine engines are provided. For example, a flow path assembly for a gas turbine engine has a boundary structure, an airfoil, and a locking feature. The boundary structure and the airfoil are formed from a composite material. The boundary structure defines an opening and a cutout proximate the opening, and the airfoil is sized to fit within the opening of the boundary structure. The locking feature is received within the cutout defined by the boundary structure to interlock the airfoil with the boundary structure.