Spikes in the serving tray anchor grilled-cheese sandwiches, keeping them upright and preventing them from sliding about.
Make long, narrow baking pans: Cut 18-inch foil pan into 4 1/2-by-17-inch piece. Fold long sides up twice by 7/8 inch. To close off ends, make 1-inch cuts along folds; fold center flap up and side flaps in. Spray with cooking spray. Repeat to make three more pans.
Preheat convection oven to 400 degrees or conventional oven to 375 degrees. Knead dough on clean surface into a smooth ball. Divide into quarters. Roll each into 3/4-by-18-inch log; trim ends to make a 15-inch log. Fit into pans; cover with sprayed plastic wrap. Let stand in a warm place until dough reaches tops of pans, 25 to 35 minutes.
Place filled pans on baking sheet; cover loosely with aluminum foil coated lightly with cooking spray. Bake 8 minutes. Remove foil; bake until lightly golden, about 4 minutes. Cool bread on rack.
Slice bread 1/8 inch thick; cut cheese to fit. Place 1 piece in each sandwich. Butter outsides of sandwiches. (Steps to this point can be done up to 12 hours in advance.) Cook on hot griddle until bread is golden brown and cheese is melted, about 1 minute per side. Serve or refrigerate up to 6 hours (when ready to serve, heat in oven until cheese melts again).