When done with a 90 Carré I think of this knot as 'cowboy drape', rather than 'knot', as it seems so much more to do with arranging the folds than knotting.
Fold your scarf into a triangle
then fold the long edge over, about 5 inches wide
gather the ends together
and bring behind your neck
cross the ends..
.. and bring them forward
From here, you can proceed in a variety of ways. You can simply tie the ends into a double knot, or use a scarf ring (moyenne size) to secure them. To see the criss-cross method, please click on the video link below.
Scarf ring used: MaiTai Collection moyenne size, light honey colour
Scarf: Hermes Cuirs de désert