A method for manufacturing sterile flexible bags filled with a filling product and provided with a valve, including a) a step of placing valves on a first flexible film and sterilizing at least one of the two surfaces of the first film, b) a step of forming bags by heat welding from at least the first film, and filling the bags with a filling product. The valves each include a base applied directly onto the first film, and a tube assembled via an open end onto base in order to cover a tapping area of the base, the tube having a removable portion intended to be removed to uncover the tapping area and allow the product to be withdrawn by poking a needle into the area.
