I'm proud to have figured this one out, after many years of mediocre pot roasts.
Secret #1: Ditch the Crock-Pot. I know, I know, the convenience. But it just does not make as good of a pot roast as. . .
Secret #2: Using a cast iron Dutch oven. On the stovetop. Which is really just as convenient. Today, for instance, I put my meat in the pot and left the house for several hours, until right before dinner. Everything was fine, just like it would be in a Crock-Pot, but oh those superior results!
Secret #3: Brown your (salt and peppered) meat in a little olive oil, remove it from the pot, then brown a cut-up onion, a red pepper, and several crushed cloves of garlic. Put the meat back in on the vegetables and add a can of broth and a cup of wine if you have it, or a beer. Put the lid on, bring to a boil, then turn down as low as it will go. The beauty of this method is the melting tenderness of the meat under the caramelized outer crust, and the magically thickened sauce that appears at the end of the cooking.
Secret #4: No more chuck roasts. It's bottom round, baby. Costs more, but has more meat and less fat. You'll throw less away, and it's less stringy, slices beautifully, and goes farther.
Secret #5: Peerless gravy. Remove the vegetables with a slotted spoon and toss. Bring the pan juices to a boil. In a small jar, shake together about 1/3 cup water and 2 T. flour. Slowly pour into pan, and stir and simmer until smooth and thick. This is truly ambrosial gravy.
Those are my secrets. Enjoy.