Separate the two sets, arranging the strands in a mirror-image pattern with the outside strands the same color and so on moving inwards. Continue knotting over each color, towards the right, until the outermost color has carried over to the middle. Now pick up the outermost color on the right side (show here in red) and make a backward knot, creating a reverse 4-shape over the 2nd color, loop it under and back through the opening. Tie a backwards knot with the two middle strands to connect the two halves. Be sure to count the number of strands so you know when to stop in the middle each time.