To make the first half of the knot you will see that I bring my left index finger from the back side of the thread catching it so that it loops around my finger this allows the thread to cross over itself. I then slide the needle under the loop from the bottom to the top on the palm side of my finger. (Note that this is to the left side of the threads crossing over.) As I slide the loop on the needle, I slide it off my finger in one motion. It sounds harder then it is.
To make the second half of the knot I bring my left index finger from the front to the back catching the thread I now bend my finger down so that the tip of my finger is toward my palm and I can see the back side of my finger. I slide the needle under the loop from the top down on the backside of my finger. Again, I am taking the loop off my finger at the same time it is going on to the needle. Again this sounds harder then it is.