An article of manufacture that has at least three layers of heat sealable material. There is at least one first heat seal between at least two of the layers in a first area effected at a first temperature. There is also at least one second heat seal between at least two more layers, where at least one of these two layers is distinct from the at least two layers joined by the first heat seal, in a second area effected at a second temperature, where the second temperature is different than the first temperature, thereby allowing for heat sealing of discrete areas of the article in discrete steps.