This is the way my Grandma, my Mom and now me do roast. It falls apart rather than slices.
1 chuck roast (you can use other kinds, but this is the cheapest and I think the best)
Prepared mustard
1 pkg Dry Onion Soup Mix
Smother roast with mustard, then sprinkle whole pkg of onion soup mix over top. Cook in crock pot on high for 5 or so hours.
To make gravy...
remove roast from crock pot and place on plate or platter. Pour drippings into a pan. Put roast back in crock pot to stay warm. Add as much water to the drippings as you want to stretch it. (I only do a cup or 2, but you could do much more). Heat until boiling, then lower temperature to medium. Add salt and pepper to taste. It will take quite a bit of each. It will taste good when you taste it. If it is blah---then add more S&P. In a cup mix some water and either cornstarch or flour, use a whisk to get rid of lumps. Add some of the hot drippings to the cornstarch or water mix to warm it up a bit. While stirring drippings with a whisk, slowly pour in the cornstarch or flour mixture. Over the next few minutes it will thicken.
To make mashed potatoes...
Boil potatoes (or use pressure cooker for 3 minutes---my favorite way because it is soooo much faster). Drain. Put in large bowl. Always add butter/margarine and S&P. Then add other dairy products like milk, sour cream, cream cheese, etc... Start mashing. I do mine by hand, but you can use a mixer instead. I like mine a little chunky, but just keep mashing until the are the desired consistency. For creamier potatoes use more of the add-ins, for healthier potatoes use less of the add-ins. You can also add shredded cheese, garlic powder, etc...