Lightly toast the sandwich bread.
Once the bread is lightly toasted, line a baking sheet with aluminum foil and spray with cooking spray. Place the lightly toasted bread on the baking sheet.
Preheat the toaster oven to 300 degrees Fahrenheit.
Top each slice of toast with 1 tablespoon marinara sauce. Next, add 1 tablespoon shredded mozzarella cheese and finally 3-4 pepperoni slices (. Repeat until all the toast is assembled.
Bake in the oven at 300 degrees Fahrenheit for 3 to 5 minutes or until the cheese is melted and the pepperoni has cooked.
Remove from the oven, slice, and serve immediately.