Heat oven to 425° F. Spread the fries on a baking sheet. Bake until golden, about 25 minutes. Meanwhile, cook the beef in a medium saucepan over medium heat, crumbling it with a spoon, until no trace of pink remains, about 7 minutes. Spoon off and discard any excess fat. Stir in the sauce and cook until warmed through, about 5 minutes. Transfer to an 8-inch square baking dish or a 9-inch deep-dish pie plate. Top with the fries and return to oven for 5 minutes. Season with the salt. Spoon into individual bowls.