Add 1/2 cup flour to a shallow dish. Combine remaining flour, beer, salt, pepper, and garlic in a medium bowl, stirring well.
Heat olive oil in a large skillet. Dredge fish in flour, then dip in beer batter. Place fish in hot oil. Cook 4-5 minutes per side or until browned and crispy. Drain on paper towels.
Preheat oven to 450. Peel potatoes and cut into french fry shape or use a french fry cutter. Toss with oil in a medium bowl. Arrange in a single layer on a parchment-lined baking sheet. Sprinkle with salt.
Bake at 450 10 minutes. Turn fries. Bake an additional 10 minutes. Check for doneness (cook time will depend on size and thickness of fries), and bake longer if necessary, 2 minutes at a time, until fries are browned and cooked through.