The only difference to the ITS video is that you're doing the braiding on a larger scale. It will take a little while to get the hang of it, because the pairs of rope need to be aligned correctly, but once you've started, it falls in place quite nicely. Assign one person to braid and the other to support the rope and untangle the 8 strands behind the braider. I got given two 60 m ropes, which would have given me a fast rope about 10 m long. However, we don't have anywhere to hang a rope that long, so we just made it out of one 60 m length to make a 5 m climbing rope. The video below should give you a sense of how to do the braid - keep reciting "two under, one over" while remembering to wrap the strands carefully so the braid looks nice and neat.