Preheat the oven to 400 degrees F.
Sprinkle the chicken breasts with a pinch of salt and pepper, and place, skin-side up, on a rimmed baking sheet. Arrange the bacon in a single layer on a wire rack set over rimmed baking sheet. Transfer both baking sheets to the oven and bake until the chicken is just cooked through and the bacon is browned and crisp, about 30 minutes.
Let the bacon cool slightly, then break each slice in half. Transfer the chicken to a cutting board, let rest until cool enough to handle and then remove and discard the skin. Cut the breast from the bone and thinly slice crosswise.
Stir the mayonnaise, hot sauce and granulated garlic together in a small bowl. Lay 6 of the toasts out on a work surface; spread each with about 2 teaspoons of the mayonnaise mixture. Top with some lettuce, 2 tomato slices, 2 bacon halves and some chicken. Cover with another slice of toast and repeat as before, spreading each slice with 2 teaspoons mayonnaise and then layering with the remaining lettuce, tomato, bacon and chicken. Spread the remaining mayo on the last 6 toast slices and top the sandwiches. Secure each sandwich with 2 toothpicks and slice each in half diagonally.