The left knot is made by knotting two threads together as follows.
Keep the left thread (orange) taut with your left hand and knot the right thread (the working thread, blue) around it with your right hand by putting it from right to left over the left (orange) thread.
Bring the blue thread to the right again underneath the orange thread and bring it to the left again on top of the orange thread.
Pull the knot tight. The first part of the double left knot is now finished.
Repeat this again to make a double left knot. Still keep the orange thread taut with your left hand and knot the blue thread around it with your right hand by putting it again from right to left over the orange thread.
Again bring the blue thread to the right underneath the orange thread and bring it to the left again on top of the orange thread. You have now made 2 knots around the orange thread, and the blue thread comes out of it on the left and the orange thread is on the right of it.
In the patterns this double left knot is shown as follows.
You can see quite clearly here that when we have to make a double left knot, that the blue thread is the right thread and that it is the one that is knotted around the orange left thread. The orange thread is the thread that will be held taut and the blue thread is the knotting thread. Also becomes clear that the orange thread comes out on the right and the blue thread on the left after making the knot. The knot itself shows as a blue knot.