Trim and discard fat from beef. Cut meat into 4 equal pieces, sprinkle lightly with salt and pepper, and coat with flour.
Pound meat with a ridged mallet until it's 1/4 inch thick. Coat with more flour, then shake off excess.
Place a 12- to 13-inch nonstick frying pan over medium-high heat. When pan is hot, add meat pieces without crowding and brown on each side, about 4 minutes total. Transfer from pan as cooked and keep warm.
Return all meat and any juices to pan. Add onion, carrots, celery, marjoram, and 2 cups broth. Bring to a boil over high heat, then reduce heat to low, cover, and simmer until meat and vegetables are tender when pierced, 20 to 30 minutes.
Meanwhile, in a 3- to 4-quart pan over high heat, bring about 1 1/2 quarts water to a boil. Add potatoes, cover, and simmer over medium heat until potatoes are tender when pierced, 20 to 25 minutes. Drain and keep warm.
With a slotted spoon, transfer meat and vegetables to a platter; keep warm.
Measure pan juices and, if needed, add water or broth to make 1 1/2 cups; return liquid to frying pan. (If you have too much liquid, boil, uncovered, until reduced to 1 1/2 cups.) Mix 3 tablespoons flour with 1/4 cup water and stir into pan. Drain any accumulated juices from platter into pan. Stir sauce over high heat until boiling, then pour over steak and vegetables. Serve with potatoes. Add salt and pepper to taste.