Combine oats, water, milk, and half the banana slices in a saucepan over medium heat. Once simmering, stir and cook until oats are creamy and have nearly absorbed all the liquid, about 5 minutes, using the back of a wooden spoon or spatula to mash banana slices as they cook.
Remove pan from heat then stir in brown sugar, flaxseed meal, and vanilla. Transfer to a bowl then top with remaining banana slices, nuts, and dried fruit.