Try leaving a bit of fat on the chuck. The fat will help keep the meat moist as it cooks. Lower the temperature of your oven slightly. You could be cooking it too quickly, so to speak. Make sure the lid is properly on the pot to retain the moisture. Baste the pot roast with its cooking juices while it cooks. Once the pot roast is cooked, let it rest for a few minutes before slicing it. This will allow the juices to redistribute. This last tip applies to almost any meat and should be regular practice.u003cbr /u003e