A method for creating a luggage bag, said method comprising the following operations: a) creating a one-piece casing having an inner surface and an outer surface, the casing being flexible, the casing having a housing and a flap, the flap being designed for placement in a folded-in position in which the casing has an interior volume and a slit extending between the housing and the flap, there being one continuous slit, and b) attaching a sealing device on the housing and the flap, at the slit.