Heat a gas grill with all burners on medium
Brush the bread with ¼ cup of the oil and season it with a pinch of sea salt and a few grinds of black pepper
Grill the bread on both sides, checking frequently, until nicely browned (~ 3 to 4 minutes per side)
When the bread is cool enough to handle, cut it into small cubes (~ ½-inch in diameter)
In a small bowl, add the shallot and vinegar and soak for 10-15 minutes
With a slotted spoon, transfer the shallot to a large bowl, reserving the vinegar.
Sprinkle the garlic with ¼ tsp. kosher salt and mash it to a paste on a cutting board with the side of a chef’s knife.
Whisk the mashed garlic, the remaining ¼ cup olive oil, another pinch of sea salt, and a grind of black pepper into the reserved vinegar
Toss the bread cubes, tomatoes, cucumber, basil, mint, capers, and vinaigrette in the bowl with the shallot