Grandma's Mushroom-Onion Brisket

Source: Grandma Lorraine
adapted by There's Always Thyme to Cook

brisket (flat cut)
1 envelope Lipton mushroom-onion soup mix
1/2 to 3/4 cup water
carrots, sliced thin
potatoes, cut in chunks
1 tablespoon flour (more or less)
Reynold's large oven bags

Preheat oven to 350 F. Put brisket in the oven bag. Add enough flour to coat the brisket so it does not stick to the oven bag. Add water, carrots, potatoes, and soup mix to the bag. Seal the bag with the tie wrap and place in a baking dish in the oven. Cook for an hour or two until the brisket is tender. Remove brisket and vegetables from the bag, slice the brisket, place it all in the baking dish and cook it for another hour or so.