To make a diamond shape, cut straws into twelve 2-inch pieces using a crafts knife. Cut a 36-inch length of embroidery floss and use the needle to string on four straw pieces, leaving a long tail at the end. Pull straws tight, shape into a diamond, and knot floss.
String two straw pieces onto the knotted floss, pushing them to the bottom of your diamond. Loop the floss around the top of the diamond and pull tight to secure the straws. Add two more straws to complete the opposite side of the second diamond.
Insert the needle back through one straw to the middle of one side where two straws meet. This is what forms the geometric shape of the ornament.
Thread the floss through four more straws to make a diamond around the center of the ornament, looping the floss around the corners to secure them. Thread the needle back through a straw to the top of the ornament and make a loop.
Tie the floss at the top of the ornament. Add a length of string or ribbon to hang the ornament.
Change up the look with a variety of straw lengths (but use the same threading and tying techniques) to make a coordinated collection of 3-D ornaments.