Abstract: Multiple flex units are used to provide predetermined focused areas of flex in a substrate, such as an equine saddle tree, Apertures are placed on the underside and filled with either a combination of stopple and slurry or slurry alone, each forming a flex unit. The placement, dimensions and fill of the flex unit enable a predetermined focused area of flex to be established within the specific area. The slurry is a mixture of carbon fibers and epoxy and the stopples are a mixture of substrate and epoxy to form hard stopples, a mixture of composite and flexible epoxy to form more flexible stopples; or a combination hard and flexible mixture in a stopples. The shape, periphery, diameter and depth each of the apertures and hardness, size and category of the stopples as well as location of placement determines the area, degree and direction of the flex.