Lightly coat an 8x8-inch baking dish with the oil. Bring the water to a boil in a large saucepan. Add the oats, cinnamon, vanilla, and salt. Cook over medium heat until the oats are cooked through, but not mushy. Transfer to the baking dish. Refrigerate overnight uncovered, to set. Remove the oats from the refrigerator and cut them into 2x2-inch squares.
Make the batter:
Place the flaxseed in a small bowl and add the water. Set aside for 5 minutes to form a gel. Then mix well. In a large bowl, combine the remaining batter ingredients except the coconut oil; mix well. Stir in the flaxseed mixture, and then pour the batter into a 10x10-inch or 9x13-inch baking dish. Dip the oat squares into the batter to coat and let soak for 3 minutes on each side. Make sure each square is coated with the batter. Use a spoon to completely coat each piece, if needed.
Melt 1 teaspoon of the oil in a large skillet over low heat. Place 3 squares of the “bread” in the skillet at a time and cook until golden brown, 4 to 5 minutes per side. Repeat with the remaining squares, using 1 teaspoon of oil per batch.
Serve warm on its own or with toppings.
Notes
Tip: To keep the French toast warm before serving, place squares on a baking sheet in a single layer in a 200°F oven.