The second strand, COMING FROM THE TOP RIGHT CORNER, passes through the first strand, under, then over twice, then under again.
After this, the strand, here shown as a thin black line, creates the design as you see it here.
(Note that the second strand, just like the first, is merely an overhand knot: this design is a combination of two overhand knots, the trick lies in how you intertwine them.)
Adjust the design in line with how closely interlaced together you want the design to be.
You could cut off the four ends of the strands and sew them upon a jacket as a fashion statement, mimicking the decorative cords once worn on military uniforms.