A method of manufacturing a plurality of packaging bags, each comprising a front wall and a back wall connected by gussets, a bottom, and a partial filling opening. The method is performed using a technique known as the transverse technique and includes steps carried out using at least one continuous strip of plastic film, as follows: • Step A: Folding the strip along its length to define a folded front wall and a folded back wall. • Step D: Inserting folds of film, defining two gussets folded in opposite directions and connected by a longitudinal edge, transversely at regular intervals corresponding to the widths of the bags between the front and back walls of the strip. • Step E: Welding and cutting the strip transversely between the two gussets of each fold to form the packaging bags. • Step F: Sealing the openings of each bag and creating at least one transverse weakening line on one of the gussets, adapted to provide access to a partial filling opening after the weakening line is broken. Before step D, the method includes the following steps: • Step B: Attaching a first strand of hermaphroditic complementary coupling means to each of the front and back walls of the strip near a longitudinal edge of the strip. The first strands are intended to be positioned facing each other when the strip is folded and are longitudinally and discontinuously attached at regular intervals along the strip from each transverse line that will become the side edge of a bag. Each first strand has a length corresponding to the dimension of the partial opening and at least half the width of a gusset. • Step C: Attaching a second strand of hermaphroditic complementary coupling means across the entire width of only one gusset of each fold. The second strand is positioned to be placed facing the first strands before step E. • Step A: Folding the strip along its length to define a folded front wall and a folded back wall. • Step D: Inserting folds of film, defining two gussets folded in opposite directions and connected by a longitudinal edge, transversely at regular intervals corresponding to the widths of the bags between the front and back walls of the strip. • Step E: Welding and cutting the strip transversely between the two gussets of each fold to form the packaging bags. • Step F: Sealing the openings of each bag and creating at least one transverse weakening line on one of the gussets, adapted to provide access to a partial filling opening after the weakening line is broken. Before step D, the method includes the following steps: • Step B: Attaching a first strand of hermaphroditic complementary coupling means to each of the front and back walls of the strip near a longitudinal edge of the strip. The first strands are intended to be positioned facing each other when the strip is folded and are longitudinally and discontinuously attached at regular intervals along the strip from each transverse line that will become the side edge of a bag. Each first strand has a length corresponding to the dimension of the partial opening and at least half the width of a gusset. • Step C: Attaching a second strand of hermaphroditic complementary coupling means across the entire width of only one gusset of each fold. The second strand is positioned to be placed facing the first strands before step E.