Use whipping twine to tie a slipped clove hitch to keep the strands together.
Two strand come towards you and one goes away while forming the knot pictured.
Each strand gets tucked under its own self once the knot is made
Do the first two tucks of each strands loosely and once it is all seated and in place, pull each strand nice and snug. Take off the Clove hitch by pulling the slipped end.
CLARIFICATION: previously a few of us mentioned tucking the first strand twice. That is when making an EYE splice. When doing a back splice as pictured above, tuck each strand one at a time.
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nick