Start by making a half knot as above.
The second half of the square knot is the reverse of the first half.
Bring the orange cord (which is now on the right hand side) behind the two core cords.
Bring it over the left hand (brown) cord.
Place the brown cord into the right hand loop by going over the core cords and under the orange cord.
Tighten by gently pulling on the knotting cord.