Actually, the purpose of the wood stock on the anchor is to turn the one arm or the other of the crown of the anchor down into the seabed so that the fluke would dig in.
Once set, the stock helped hold the crown perpendicular to the seabed. Which improved the hold of the anchor on the ground. Depending upon which navy and which tradition is being followed, the anchor line is payed out with "scope"--which would be from 1: 5 to 1:7 So, in ten fathoms' of water, 50 to 70 fathoms of anchor cable would be payed out. This length of line is enough to have a good portion horizontal along the seafloor.
This is also why a buoy is lashed to the crown of the anchor to float above the set anchor. If the anchor set into rocks or a sticky mud bottom, after heaving the anchor cable in, the captain could "fish" the anchor by heaving up on the buoy line, to break the anchor out (or twist it out of the rocks).
With the anchor broken loose from the bottom, the entire weight was born by the messenger to the capstan, and the anchor would be "aweigh" which allows the ship to get under way .