molding a plurality of separate pieces of closed-cell foam into a single-piece molded foam article by exposing the plurality of separate pieces to a temperature cycle within a sealed mold sufficient to soften the plurality of separate pieces without fully melting the closed-cell foam and allow the plurality of separate pieces to physically bond to each other, wherein, during the temperature cycle, the sealed mold is unsealed at least once, releasing gases and/or pressure from the mold, wherein unsealing the sealed mold includes, upon an average temperature of the plurality of separate pieces of the closed-cell foam reaching a minimum threshold temperature, stabilizing the average temperature, and then opening the sealed mold, forming an unsealed mold;

holding the unsealed mold open until a pressure within the unsealed mold reduces to within a threshold of atmospheric pressure, and then closing the unsealed mold to re-seal the unsealed mold, forming a re-sealed mold, and cooling the plurality of separate pieces of the closed-cell foam in the mold to a second threshold temperature, the second threshold temperature lower than the minimum threshold temperature;

forming the single-piece molded foam article by physically bonding the softened plurality of separate pieces bonded together without an adhesive, and, following the releasing, removing the single-piece molded foam article from the mold;

wherein the single-piece molded foam article is the cushioning element for the article of footwear.