You will need a sturdy snap of some sort, strong enough for the weight of the dog you are using it for. Then two pieces of 550 paracord at least 25 feet long, giving you a leash about four feet long. I sometime just get the 50' cord and cut it in half no measuring that way! Also you can use two different colors to make the leash and it looks really good.
Starting is the hard part on this project.
The way that this leash is made it has a little spring to it when pulled, so doesn't just completely jerk your arm off if the dog tries to take off all of the sudden. SQUIRREL!!
Start by holding the snap in one hand and take your two pieces of cord, going through the eye of the snap, try to get the snap as close to the center of the two pieces as you can. Leaving about half of each piece on either side of the snap. You might want to make a mark so you know where center is. Now make an "X" shape with the two cords.
Now take the top left piece and fold it down over the other left side piece. Continue doing this until you get to the fourth piece. Going counter clock wise or clock wise just start on the right side. Now take the fourth piece and tuck it through the loop of the first piece and pull all of the pieces as tight as you can. You might want to enlist some help or secure two of the pieces that are across from each other, so you can get it really tight. Now repeat going left, right, left, right, or right, left, right, left depending on how you started, until you get about 10 to 12 inches from the end.
Now you can finish with a lanyard knot like I did or you can figure out a different way to tie it off and make a handle. I used the one from here:
I did a lanyard knot using two of the cords and wove the other two through the center. Then I took two of the cords, twisted them together into two sides for a handle and finished with another lanyard knot, using the two longest pieces for the last knot. Now put a little spot of super glue in the middle after pulling the remaining two pieces through the middle and your set.
Again any suggestions on how to make or explain this better are welcome! Thanks!