Step 1: In a blender, puree 3/4 cup loosely packed flat-leaf parsley leaves and 2 scallions including green tops, chopped with 2 tsp lemon juice, 2 tbsp cooking oil, 1/4 cup water, and 1/4 tsp each salt and pepper. Step 2: In a medium saucepan, bring the 2 cups water to a boil with 3/4 tsp salt and 1/4 tsp pepper. Stir in 3 tbsp of the parsley puree and 1-1/3 cups couscous. Cover, remove from the heat, and let sit for 5 minutes. Step 3: In a large nonstick frying pan, heat 2 tbsp oil over moderately high heat. Sprinkle the flounder with 1/4 tsp salt and 1/4 tsp pepper. Dust the flounder with flour and shake off any excess. Sauté the fish until brown and just done, about 2 minutes a side for 1/2-inch-thick fillets. Serve the fish on the couscous with the remaining parsley puree on the top.