Preheat oven to 300° F. Lay bread slices in one layer on a baking sheet. Bake the slices for 6 minutes to dry them slightly, then flip and bake for 6 additional minutes. Set aside to cool. Reduce the oven temperature to 200° F.
Whisk together the eggs, half-and-half, granulated sugar, cinnamon, vanilla, and salt in a large casserole dish.
Heat a large nonstick skillet over medium-low to medium heat. Place 2 slices of bread in the egg mixture. Let the bread completely soak in the egg mixture on both sides, about 30 seconds to 1 minute total, checking after 15 seconds. (Bread should feel heavy and soaked through but hold its shape without breaking apart.) Melt a tablespoon of butter in the skillet and add the 2 soaked slices; cook until the outside is golden brown and crisp and the inside is cooked through, 4 to 5 minutes per side. You will need to watch and adjust the temperature between medium and medium-low if the bread is browning too quickly or not browning fast enough. Keep finished French toast slices warm on a rack nested in a rimmed baking sheet in the oven. Repeat with the remaining slices.
Serve with a dusting of confectioners' sugar and a drizzle of maple syrup.