What you want to do is cut two equal length pieces of assist cord. These pieces need to be approx 1.5 to 2 x the length you would regularly use for tying assists ( like I said, it uses a fair amount )
Thread both sections of the Kevlar through the spilt ring to equal length:
Next step, once you have plaited a section long enough, is to thread all 4 tag ends in through the hooks eye. Make sure to use proper jigging hooks with the kinked eye, and thread the tag end into the eye from the hook point side:
Once you have threaded the Kevlar round into the knot, make sure all the strands are lying neatly and then start snugging them down one by one:
You should end up with something looking like this before you really tighten it down:
You then can trim the tag ends of the 4 strands of Kevlar, and finish it off with a small section of Heat shrink over the tag ends to neaten it up if you wish, or leave them as is.
Below is an example of two finished Assists.
The Top one is using 240lb JigStar Kevlar and the bottom is using 200lb Jigstar Kevlar:
A close up of the 240lb rig:
And a shot of the two showing the plait: