The handle is cut out, or skeletonized. The cord is woven in and out ( from both sides), wrapping around the previous strand. Once you have the first plait done, the rest is just repetition.
I will try and describe it in words,as far as I can guess the procedure, but it looks pretty basic:
The cord starts with the center of the piece of cord over to top at the front.
Bring the ends down ,around, and back through the open center ( from each side).
Go under ( around) the previous cord, over the top, and down through the center.
Continue going under the previous cord, around the edge, through the center,.......
Keep the order of the cords 1-2-1-2-1-2 as they go around the top and bottom so it all looks evenly plaited. An easy way to keep the ends straight is to make one red and one black with a sharpie.
When you reach the end,bring one end out on the top, and the other out on the bottom.
Wrap one end round and round the end of the metal tang. Once it reaches the other side, pull it through the plaiting and tie in place temporarily. Then, take the other end and make the same wrapping loops, going between the previous loops. Pull tightly as you go. Once you reach the end, pull it through the plaiting along side the other loop, glue with a dot of super glue, and trim flush.
Note - If there isn't enough room for the second looping to make it without bunching up, pull a few of the first end's loops out .
That may not be the exact procedure, but it should get you started in figuring the plait out. A little trial and error should get you a nicely plaited handle.
A way to estimate how much cord it will take to plait the handle is to wrap the cord tightly around the tang from the ricasso to the butt. You will need approx. three to four times that length. Try four times on the first time you plait it, and see how close the estimate is . An ancient plaiting proverb is:
"It is far easier on one's soul to waste 1 foot of cord than to wish for 1 inch of cord".
Some other tips:
Before you start, to make the plaiting easier, pull the cord ends tight, and apply super glue for about 2", letting it cure under tension. When dry, cut the ends cleanly to make Aglets from the stiff ends ( Aglets - your word for the day - Thank you Rosemary Rae). A pair of hemostats is also very useful in pulling the ends through the bights.