Peel and mince or crush the garlic and add it to the olive oil in a measuring cup or small bowl. Add in the salt and stir to combine. Set aside.
Slice the bread horizontally to create two flat pieces for your open-faced sandwich. If the top is too rounded to lay flat on a surface, slice off a thin layer.
Slice the tomatoes and fresh mozzarella
into even-sized rounds.
Thinly slice the basil leaves, creating a chiffonade.
Preheat the grill over medium-high heat.
Add the bread to the grill, close the lid, and toast 1-2 minutes per side. Remove from heat.
Reduce the heat on the grill to medium.
With the toasted bread sliced side up, assemble with cheese and tomatoes. Top with basil.
Return the open-faced sandwich to the grill, close the lid, and let cook for 8-10 minutes, until the cheese has melted, the tomatoes and basil have softened, and the bread has toasted.
Remove from heat and slice into 6 rectangular pieces to serve as a main dish or 12 squares to serve as an appetizer.
Lightly drizzle with some balsamic reduction and serve.