Preheat oven to 375 degrees. Butter the inside of an 8 x 8 glass baking dish.
In a large bowl, combine oats, rye flakes, half of the almonds, baking powder, cinnamon and salt.
In a second bowl, whisk together maple syrup, milk, egg, butter and vanilla.
Sprinkle 1 cup of the berries in the bottom of the prepared dish. Top with dry oat mixure.
Pour wet mixture over the top of the oat mixture. Tap the pan on the counter a couple of times to make sure that the wet mixture sinks all the way to the bottom and that the dry ingredients are completely submerged .
Sprinkle remaining berries and ¼ cup of sliced almonds over the top. Bake until golden brown and oats are set, about 40-50 minutes. Serve warm with optional toppings.