Page 53 - Peter Randall "The Craft of the Knot.."

STEP 2 Next, separate the standing parts, moving one of them (the one
at the end of the rope that did not form the loop) under the looped

running end and over the other running end.

STEP 3 Use the same rope’s running end to make the final tuck.

STEP 4 Tighten down the knot, leaving short running ends to stick out
perpendicular to the ropes.