Make sure you're not accidentally tying the Granny Knot instead!
Start with two pieces of rope the same size, coming from opposite directions.
(This picture is inverted compared to the rest of the series. Sorry!)
Fold one rope over the other one, so that one loose end ("tail") goes up and the other one goes down.
Take the end that bent down, and bring it behind the other rope, and up.
This is the basic "tent" that we use to tighten shoelaces or a knot holding a package closed.
Take the loose end that is behind the twist, and bring it behind the other loose end.
One rope is behind both on the top and the bottom; the other rope is in front both on the top and the bottom.
(This is the critical step in getting this knot right.)
Take the rope that is in front, and bend it over the other rope, pass it through the loop, and pull it back in the direction it came from.
Note how each loose end of rope is exiting the knot next to the piece of rope it came from. The ends are smooth and parallel.
Tighten the knot by pulling on the loose ends.
As you tighten the knot, the loose ends will stay parallel to the fixed ends.
This is how the finished knot looks. No matter how hard I pull on the fixed ends, the knot stays stable and the tails stay close to the fixed ends.
This is how the knot looks from the other side.