In a small bowl combine the butter, lemon juice, seasoning, garlic, and thyme.
Prepare the grill for direct cooking over medium heat (350° to 450°F).
Cut eight sheets of aluminum foil, each about 12 by 20 inches. Line an 8-by-8-inch cake pan with two sheets of aluminum foil, arranged in a crisscross pattern. Layer the bottom of the foil-lined pan with the sliced potatoes (this will help insulate the shellfish and keep them from overcooking). Top the potatoes evenly with the shrimp, clams, sausage, and corn pieces. Drizzle each packet evenly with the butter mixture. Close the packet by bringing the ends of the two inner sheets together, folding them on top of the filling and then bringing the ends of the two outer sheets together, folding them down. Repeat this procedure with the remaining packets.
Grill the packets over direct medium heat, with the lid closed, until the clams have opened, the shrimp have turned opaque, and the potatoes are cooked, 20 to 25 minutes. To check for doneness, using tongs, gently unfold one of the packets and carefully remove a potato, being careful not to puncture the bottom of the foil. Using a knife, gently pierce the potato to ensure doneness. When everything is cooked, remove the packets from the grill. Carefully open each packet to let the steam escape and then pour the contents into warm bowls. Serve immediately.