In Switzerland at Christmastime it is traditional to make decorative stars from field straw. Jack Kuntz, a New York commercial artist, admired these ornaments so much he determined to duplicate them at home.But field straw was hard to find in New York and Mr. Kunz decided to try soda straws. They worked beautifully. To make a star takes 75 straws and 60 yards of crochet cotton. The dexterous can make a star in three hours; a butterfingers takes longer. The stars have 20 points, are built on an icosahedron, which sounds worse than it is.