Add the apples to a large bowl. Pour the granulated sugar, 2 tablespoons (16g) of flour and cinnamon over the apples and toss until all the slices are evenly coated.
Spread the sliced apples evenly in a 9 x 13” glass dish. Pour ¼ cup water evenly over the top gently moving the apples around in the pan to coat them.
In a medium mixing bowl combine the oats, remaining cup of flour, brown sugar, melted butter, baking powder and baking soda together.
Crumble the mixture evenly over the apples. Bake the crisp until the top is golden brown, about 50 to 60 minutes.
Let cool for about 10 minutes. Slice the warm apple crisp into squares and use a spatula to scoop into bowls topped with vanilla ice cream. Serve warm.