A packaging container for holding contents such as fresh food. The container comprises a tray having a flange, a pre-formed scaling ring and a flexible film for sealing in the contents of the tray. The sealing ring is made from fiber, filament or tape (“FFT”) that is shaped into a shape that matches the shape of the tray flange. The sealing ring is adhered to the tray flange by heat welding or other means and the flexible film is adhered to the sealing ring.