Recipe courtesy of The Bear Cupboard (http://bearcupboard.blogspot.com)
1 whole dressed flounder with head and tail, about 1-1/2 lbs.
1-1/2 tsp. kosher or sea salt
1/2 tsp. black pepper
1 medium sweet onion, peeled, thinly sliced
1 lemon, thinly sliced
3-4 sprigs fresh parsley
Soak plank in a clean sink with warm water for at least 5 hours. Weigh down with a gallon jug of water or a brick wrapped in tinfoil.
Heat gas grill to 400-425F. Turn one burner off and maintain grill temperature at 400 - 425F. Remove plank from water, drain. Rinse fish under cold running water; pat dry with clean paper towels. Approximating where fish will be on the plank, place onion and lemon slices and sprigs of parsley. Sprinkle fish inside and out with salt and pepper.
Stuff fish cavity with onion and lemon slices and sprigs of parsley. Place fish on plank over lemon and onion slices. Tuck any stray lemon and onions slices under fish. Use remaining onion and lemon slices for top of fish.
Place planked fish on turned-off burner; cover grill; cook about 40-45 minutes,or till fish skin is dry and papery and fish is cooked through. You can check that the fish is cooked through by inserted a fork through the skin into the flesh. The plank should not catch fire when used on a turned-off burner. In the rare event that the plank should catch fire, just wet edges with a Tbsp. or two of water. Transfer plank using grill mitts and tongs. Let rest 5-10 minutes.
To serve: Peel back skin; remove.
With fork, gently push fish away from the center of the bone towards the outside, exposing the bone.
Lift the bone and remove, exposing the bottom section of the fish.
A 1-1/2 lb. whole fish will serve 2-3 people. Leftovers are delicious the next day, cold or heated.