I've got a big chuck roast in the oven right now. I used 1 package of onion soup mix (yes, I know it has carbs, but even if I were to consume 1/4 of the pan juices, it would give me 5 grams of carb) and 1/2 cup of water. Cook it covered in a slow oven (about 325 degrees) for 3 or 4 hours. Tender and juicy every time.