In its simplest conceptual form, the applicant's invention is the structure of a conventional shoe sole that has been modified by having its sides bent up so that their inner surface conforms to a shape nearly identical but slightly smaller than the shape of the outer surface of the sides of the foot sole of the wearer (instead of the shoe sole sides conforming to the ground by paralleling it, as is conventional). The shoe sole sides are sufficiently flexible to bend out easily when the shoes are put on the wearer's feet and therefore the shoe soles gently hold the sides of the wearer's foot sole when on, providing the equivalent of custom fit in a mass-produced shoe sole. This invention can be applied to shoe sole structures based on a theoretically ideal stability plane as a basic concept, especially including structures exceeding that plane. The theoretically ideal stability plane is defined as the plane of the surface of the bottom of the shoe sole, wherein the shoe sole conforms to the natural shape of the wearer's foot sole, particularly its sides, and has a constant thickness in frontal or transverse plane cross sections.