This is an adaptation of tying a bowline knot. Some say this is like the weaver's knot; others don't. I don't really care; it works and I think you'll like it.
Make a 6 out of the yarn coming from the loom having the loose end on top of the 6. Yes, I made my 6 the other way!
The yarn being tied on is the "rabbit."
Now, for the fun part.
The rabbit comes up the hole, around the tree and back down the hole.
Grasp both ends of the "rabbit" yarn plus the end of yarn from the loom and pull. What do you know? A knot that will (k)not (; come loose.