Place your scarf (a 90 Carré) face down on a flat surface and pinch some silk in the place where indicated:
Make a simple knot (or use a scarf ring, as illustrated further down):
Make the knot as small and tight and possible:
Now place your scarf in front of your body, the knot facing inwards. Take the upper ends (indicated by pink arrows) and secure them behind your neck with a small double knot.
Take the lower ends and tie them behind your back with a small double knot.
Instead of making a knot in step one, you could also use a scarf ring (petite size) to gather the silk:
Pinch some fabric..
and feed through one end of the ring
pull to gather more fabric
then feed through the other end and tighten
A tight and secure fit is important, if the outcome is loose, go back to step three and pull more fabric through