My mom made a killer potroast and it's one of the few of her recipes I learned to make, since I wasn't much interested in learning to cook when I was younger. It's my “go to” date recipe, how I woo a woman, unless the woman I am trying to woo is a vegetarian in which case I'm a little bit of luck.In any case, the procedure is actually fairly simple. The real key to cooking a potroast is to get a well marbled bit of meat. What you're actually looking for is going to be called a chuck roast. Unfortunately the war on obesity is also the war on potroast, so you might not be able to find something like at your local grocery store. If you can't, go to another grocery store that is not as nice as the one your normally shop at. They will probably have it.
Use a heavy bottomed large frying pan or roasting pan, sear all the sides of the meat using either a browning sauce or that Braggs stuff (I forget the exact name but I am sure you know what I mean) as well as a little olive oil. Once the meat is seared everywhere, put in a slow cooker on the very lowest setting you can find. The slower you cook potroast, the more tender it will become. You definitely never want it anywhere near a full boil; my mom used to mimic the slow cooker with a pan of water on the stove but that's a really delicate situation.
Add potatoes and carrots and, if you like, a few small pearl onions a few hours into cooking. If they get done before the potroast, just remove them and store until you're ready to eat. The potroast is done when you stick a fork in it and it falls apart. You can make a gravy but don't bother. The juice is plenty enough.