How can I change the flute or grain direction of a drawing layer?

The easiest method is to use the direction indicator at the bottom of the drawing canvas. You'll see a series of indicators including attributes such as machine direction, flute\grain direction, print face\die face.  The flute\grain direction features two small parallel lines.  Click the indicator to toggle between flute\grain top-to-bottom and flute\grain left-to-right.