Heat oven to 400°F. Cut four 18x12-inch sheets of heavy-duty foil. Dry flounder fillets with paper towels. Place each fillet in center of sheet of foil. Sprinkle each with thyme and chives; top with lime slices.
Spoon vegetables next to each fish fillet. Top each with 1/2 teaspoon butter. Wrap each packet securely with double-fold seals, allowing room for heat expansion. Place on 1 large or 2 small cookie sheets.
Bake at 400°F. for 15 to 20 minutes or until fish flakes easily with fork and vegetables are thoroughly heated.