Preheat oven to 350 F. Combine the tomatoes, garlic, olive oil, ½ teaspoon salt, and pepper in a large bowl. Spread onto a parchment paper-lined baking tray, and roast in the oven for 45 to 55 minutes, or until the tomatoes have burst and are browned.
While the tomatoes are in the oven, cut the bread about ¼- to ½-inch thick slices, and place on a baking tray. Bake for about 10 minutes before the tomatoes are done.
Top the slices bread with the tomatoes, basil slivers, a drizzle of balsamic vinegar, and more olive oil if desired. Top with the remaining salt or flaky salt, if desired.