links to instructions:
http://delawarequilts.com/BOMs/3DimensionalBowTie.html
http://www.quiltmag.com/proj-tips-bowtie.php
i like the first set of instructions better.
one hint: it's easier to get the finished block into shape, press flat, and make the knots square if you don't sew all the way across the final seam. leave about a 1" gap in the center. (this also leaves a nice little hole if you decide to stuff the bows.)