Decorative frogs can be made of purchased cord or of self-fabric corded tubing. Pin the frog into the desired design, sucuring each loop with small stitches on the underside. Slipstitch the frog to the garment, leaving one loop extending beyond the garment edge for buttoning. Chinese ball buttons are commonly used with frogs and can be made of the same cord.
The size of the ball will depend on the thickness of the cord.
About 8 to 10 inches of a 1/4" cord makes a small button.