A method of making a multiple ply slotted partition for use in a slotted partition assembly is provided. The slots of the partitions are engaged with each other at a plurality of intersections. The partitions are made by folding over a partition blank and securing a foam portion of the folded partition blank to itself. The foam may be heated before being cooled to secure opposed plies of the multiple ply partition together. The opposed plies of the partition are fused or parent welded together.