Now, the other problem with sous vide is the sealing process. The food must be sealed off completely from any outside air, so this means you need a vacuum seal. The easiest way I've found to accomplish this is to put a pad of plastic wrap in a bowl or container, then put your food on top of it. Then place a lid on top of the food and the bowl/container. This will create a vacuum, and the plastic will keep the air in the vacuum. You can't use a lid that isn't made of plastic because if it's not fully plastic it will flex and let air in.
The temperature in the bath is set to your desired internal cooking temperature. If you're at room temperature, you'll need to adjust your set points so that your target internal temperature corresponds to the lowest setting of the slow cooker you're using.
This sous vide cooking method is a great way to cook perfectly, but it doesn't get all the glory. Traditional steakhouse or other restaurant-style cooking gets the glory and recognition of many, especially from America's top chefs. But sous vide steaks and other meat doesn't get the respect it deserves, even though it is just as good.
A sous vide cooking method is one that is done at a very low temperature, usually around 70-75° F. You can cook your steak at your preferred doneness temperature. You can have it cooked just right.
What is the perfect doneness temperature for steak? Well, it depends on the cut of meat, on the cut of the muscle fibers, and on whether it's a medium or well done cut. But for most steaks, well done is the right temperature. Proper cooking in an sous vide lets the meat cook just right, but not so far into well done that it becomes dry and tough.
You can't get the same texture and flavor as the old school steakhouse, but you can get a steak with the same texture and flavor that will be much more tender, juicy, and flavorful than the one you'd order in most restaurants. This video from PBS has an awesome visual demonstration of how sous vide steak can be so tender compared to a regular cooked steak.