Slip the loop end of double-line leader through the eye of swivel.
Rotate the loop end a half-turn to put a single twist between loop and swivel eye.

Pass the loop with the twist over the swivel.
Hold the end of the loop, plus both legs of the double-line leader with one hand.
Let the swivel slide to other end of double loops now formed.

Still holding the loop and lines with one hand, use your other hand to rotate the swivel through center of both loops, at least six times.

Continue holding both legs of the double-line leader tightly, but release the end of loop.
Pull on the swivel and the loops will begin to gather.

To draw the knot tight, grip the swivel with pliers and push loops toward the eye with fingers, while still keeping standing lines of the leader pulled tight.