Cut from above the shoulder blade. The roast is a thick crosswise slice. The Flatiron Steak is produced by cutting the roast in half horizontally into upper and lower halves to remove a membrane. This is the most tender of the chuck cuts, and the Flatiron has been the most successful of the "New Steak" cuts.
The photo specimen, a Flatiron Steak, was 13-1/2 inches long, 4-1/2 inches wide and 1-1/4 inch thick for the thick half and 1/2 inch thick for the thin half. Weight was 1 pound 13-1/8 ounces. This made reasonably tender steaks.
The purpose of the "New Steaks" is, of course, to separate consumers from their money. The traditional well known steaks have become so expensive beef consumption has been falling, even as carcass costs continue to rise. Marketeers are attempting to come up reasonably tender steaks from the tougher sections of the beast, because they can be sold at a lower price than the well known ones. That price is, however, higher than that for ground beef, which is what much of these sections might otherwise end up as.
More on Cuts of Beef.