Things you'll need:
 String or ribbon
 Felt (use fabric if you'd like)
 Roller cutter
 a Ruler
Using a cardboard stencil, I cut several diamond shapes out of the felt. The stencil was 2" wide and 4" long. A 9x12 inch sheet of felt yields about 16 full diamonds. 4 sheets of various colors make about a 10 foot long banner.
Place the string in the middle of the diamond and fold it over. Stitch through the string, down the felt to the point and back up the other side. Space the flags about an 1" apart and repeat. (an alternative would be to sew a straight line on the opposite side of the string as the fold- leaving the two points open)
For a No-Sew option: use Felt glue to bond the felt together folding it over the string. Felt Glue is non-toxic, has no odor and dries totally clear. It bonds without soaking through, dries quickly and easily cleans up with water.(I haven't actually used this glue, but Elmer's white glue absorbed into the felt.- If anyone knows of a better glue- please leave a comment. Thank you)
Tie a loop on each end of the string to finish. Hang & Celebrate!