How-to Make a Diagonal Napkin Fold
Place a square cloth napkin wrong side up on a flat surface. Fold in two sides so they overlap and form a rectangle.
Fold the upper left corner down to the center of the rectangle’s lower edge.
Fold the triangle you just made over so that it forms a square.
Turn the napkin over; roll two sides into the center to make a tube. Turn the napkin over so the rolled edges are underneath. Slip a wristwatch over the napkin.