Described are a mold and molding process for manufacturing devices and containers that are scalable, modular, and lockable laterally and vertically with other like devices or containers. The mold is formed with a cup mold and top end mold sections specially designed to allow for molding and demolding a container with an undercut. The cup mold includes, on a vertical wall, one or more undercuts. Multiple undercuts may further form tongues with undercuts each of which forms a groove with undercuts on the molded article, and/or one or more grooves with undercuts each of which form a tongue with undercuts in the molded article. Molding and Demolding of the article with undercuts is further enabled by utilizing an improved method of molding said article with an undercut, and demolding said article from the mold once it is molded, by improvements to each stage of the molding process, including the preform stage, the conditioning station stage, the blow stage and the release stage.