Tie the hook first, double up the other end after having passed it around & taken it off a pin to ensure correct length, form a double overhand loop knot LOOSE (so don't tighten it down), pass the loop around a pin of the diameter/size you want and then, importantly, put a needle into the actual knot and slide it to where you want it as you tighten the loop knot down. This ensures the loop knot doesn't tighten down prematurely making a loop which is too big. Then pull the needle out and finish tightening.