There are cuts of meat known as restaurant cuts, because they are tough when not handled properly, but have plenty of flavor if cooked in the right way. Among these cuts are hangar steaks, flank steaks, skirt steaks, and flatiron steaks. The flatiron steak is well described here, and as the local Kroger has been offering this cut for 6 and 7 dollars a pound, I was curious how well it handled via sous-vide.
Kroger sells this steak in 1.5 pound sealed packs. I bought one, sliced it roughly into 4, vacuum sealed the meat, and froze it. This particular example sealed the most poorly; you can see some air in the pack. This will tend to make the plastic float. Just take the pack and shake it a little, once unfrozen, so the air pushes one end of the plastic up and the steak can sink into the pool of water. You don’t need total immersion, just temperature equalization, but in my case, a little shaking allowed the whole of the steak to go under water.
Five and a half hours later, 30 seconds of sear a side, some spices, and the steak looked like this. There was some chew, some mouth resistence, but no toughness. The steak was pleasantly tender.