The invention relates to a method for manufacturing (S) a bag (3) by means of blown film extrusion, including the following steps: extruding (S2) plastic such as to form an annular film (2) including closing assemblies (10, 20), said annular film being intended to form the walls of the bag; and blowing (S5) the annular film such as to form a sheath, the complementary profile sections (14, 24) of each of the closing assemblies (10, 20) being integrally formed with a base (18, 28) connected to the annular film (2) via a connection rod (19, 29) that extends parallel to the longitudinal axis (X) between the annular film (2) and the base (18, 28) and is designed to keep the base (18, 28) separated from the annular film (2).