It looks like a bowline knot is used at the end of a rope. Can a bowline be tired part way down the rope? I use 300' of rope and I don't always let all of it out.
Yes. Make a loop in the load end of the anchor rope. Instead of sticking the very end of the rope thru the loop, double up the rope where you are tying, creating a bight, and tie with it, after you have gone around the cleat base or thru the shackle.