I'm posting this here so I can remember what I did.
After trial and error, this is my perfect pot roast recipe.
This is for a chuck roast. I don't know the size of mine but it was $12 at Walmart.
(ETA: The recipe says 4 lbs.)
Salt and pepper both sides of roast.
Brown roast in oil in pan until brown on both sides.
Put in slow cooker with 1 cup water and an onion, cut in large chunks.
Cook on high for 3 hours.
Add about 15 baby carrots, I piled them up in the middle of the top of the roast.
Add 8 potatoes, peeled and cut in half.
Arrange all around the side of the slow cooker. Salt and pepper again.
Cook 3 additional hours on low. (Check after 2 hours.)
Pull roast apart with 2 forks. If it pulls apart easily, it is done.
Add more salt and pepper to taste, put on "keep warm" until you are ready to eat.