My husband is crazy about this and can eat about 5 at one sitting. You can change the amounts to suit your taste and size of the roast if you want. This is a versatile dish. Hope you enjoy it as much as we do.
Put chuck roast in crockpot. Add all ingredients in any order you wish. You can adjust the ingredients to your taste and according to the size of the boneless chuck roast. I don't measure anymore so it's just to your taste. Cook on low for 8 to 10 hours, depending on the size of roast you buy. A smaller roast can take 6 or 7 hrs.
When roast is done, take it out and put it on a plate. Turn crockpot off. Put some cornstarch in a bowl and whisk in some juice from the roast until thickened. Pour this into the crockpot and stir until a gravy is made.
Shred the roast and add to gravy and stir. You can shred the roast with your fingers if it has cooled. That way you can pick the fat out and discard. Use a fork to shred if roast is still pretty hot. Salt and pepper as you like. Serve on flour tortillas.