Personally adjustable footwear with at least one sole layer including: a toe portion, a heel portion, and an intermediate portion. The intermediate portion has openings passing vertically through the layer so that the intermediate portion is elastically flexible to allow relative longitudinal displacement of the toe portion and the heel portion to vary a length of the layer without significant variation in a thickness of the layer. A retention mechanism selectively fixes the toe and heel portions in any of a number of relative positions. Also disclosed are implementations with insertable and removable segments, and with elongated elements sliding in channels.