The rules for box and whisker plots will be part of the Tactile Graphics Guidelines which is now in Draft form.
The number line of a box and whisker plot is the only part that can be composed of braille dots -- use number line rules. The actual box and whisker must be tactile -- drawn as it looks in print. Don't put any text between the box and the number line, with the box being 1/4 inch above the number line. Regardless of their placement in print, boxes must be moved above the number line.