A method of manufacturing flexible containers that are hermetically resealable. Each resealable container comprises a receptacle and a pair of plastic zipper strips. The zipper strips are flattened at the ends within the side seal regions and are joined to each other, without substantial deformation of the closure profiles, in respective transition areas substantially contiguous with the side seals. These transition areas of zipper strip joinder assist in providing a leakproof transition from the openable section of the zipper to the side seals, where the closure profiles are fused and flattened (i.e., crushed).