1. Preheat the oven to 425º.
2. Grease a 9 x 13 pan.
3. In a large bowl, combine the oats, flour, brown sugar, baking soda and salt and mix by hand.
4. Stir in the melted butter and vanilla until thoroughly combined.
5. Press the mixture evenly into the bottom of the 9 x 13 pan with your fingers.
6. Combine the flour, brown sugar and butter into a new bowl and use a fork or pastry blender to mix.
7. Continue to mix until it resembles large crumbs.
8. Set aside the mixture until later.
9. Place the blueberries into a new bowl and toss them with the almond extract.
10. Pour the blueberries evenly over the bottom layer in the 9 x 13 pan.
11. Combine the sugar and flour and sprinkle it evenly over the blueberries.
12. Sprinkle the top layer evenly over the blueberries.
13. Bake for 15 minutes at 425º.
14. Lower the oven temperature to 350º and bake for another 20 - 25 minutes until the top is golden brown and the edges are starting to brown.
15. Let the pan cool on a wire rack and then store in a cool place or the refrigerator.