"In still another aspect, a method is disclosed for manufacturing a sealed package for use in a self-heating assembly that produces heat by causing a liquid reactant to react exothermically with a solid reactant to heat a product. More specifically, the sealed package has an outer container, a lower support structure within the outer container, a layer of solid reactant above the lower support structure and within the outer container, an upper structure above the solid reactant and within the outer container, and the upper layer that is permeable to liquid and that extends across an otherwise open top of the outer container above the upper structure. The sealed package of claim 1, wherein the layer of solid reactant above the lower support structure is a layer of non-granular solid reactant. [Extracted from the article]