Here's how you make the single version...
This braid requires 4 strands each of three colors (blue, yellow and black in the diagrams.) Set them up like this:
Interlace the middle four (black) strands, and create a shed by lifting up every other blue and yellow strand.
Pass two black strands through each shed, so that the black strands move from center to edges, two on each side.
Change the shed in the blue and yellow strands. Interlace them in the center by laying down the three strands in the bottom shed on the right, then the three strands in the bottom shed on the left. Continue by putting the top three strands from the right on the pile, then the top three from the left.
Change the shed in the blue and yellow strands and pass the black strands back through from the outside to the center.
Repeat these steps.
A wider braid can be made similarly, just using more sets of strands, for
example a double width braid might be set up:
B B Y Y B B K K K K B B Y Y B B K K K K B B Y Y B B
The photo shows a double-width braid. Follow the over-under interlace patterns as in the picture.