The present invention is directed to a method forming a bottom-gusseted package, wherein each package includes an inwardly-extending, pleat-like gusset at the bottom of the package. To permit heat-sealing formation of each package, the sleeve from which each gusset is formed comprises a lamination of two differing polymeric materials, so that only an exterior surface of each sleeve exhibits the desired heat-sealing characteristics. To facilitate package formation, the sleeves from which the bottom gussets are formed are maintained in a temporarily closed or sealed configuration during package formation by providing a preferably frangible bond or seal at the edge of each sleeve. This result is preferably achieved by folding the laminate material, and temporarily sealing or joining an outer layer of the laminate material from which gusset is formed, while an inner layer is maintained in an unsealed condition.