I recently finished a hammer head to forge blades and to do general blacksmithing. It is my preferred size a hair over 2 lbs. The first picture is the stock similar to what I start with. Actually this piece of tug boat or rail road chain link is for a 3 lb hammer. Either way, its round stock about 6 inches.
I have to upset the section, making it shorter and fatter by squishing it end to end. This allows me to start squaring it to about 1 1/2 inch square X 4 1/2 or so. I then drill three small holes about 1/4 inch apart where the eye is going to be. This gives the punch/drift a path to travel as it goes through the head.
I do a lot of hammering, adjusting, hammering some more, grind a little, and then heat treat it. Here it is while its still hot.
This is the finished head.