Preheat the oven to 400˚F (200˚C). Line a large baking sheet with parchment paper.
In a large bowl, whisk together the all-purpose flour, almond flour, baking powder and salt. Using the large holes of a cheese grater, grate the butter over the top of the dry mixture (alternatively, use a box grater to grate the butter onto a piece of wax or parchment paper, then transfer the butter to the bowl). Place the bowl in the freezer for 10 minutes to chill.
In a small bowl, whisk one of the eggs with 1 teaspoon of water. Set aside (this will be the egg wash for later).
In a separate bowl, whisk the remaining egg with the sugar, buttermilk and almond extract until smooth.
Take the bowl out of the freezer, and toss the butter with the flour mixture until evenly incorporated. Make a well in the center of the bowl. Pour in the wet ingredients and add the blueberries. Slowly work the dry ingredients into the wet ingredients until mostly incorporated but still shaggy and floury (you’ll finish bringing it together in a minute).
Scrape the dough out onto the parchment lined baking sheet. Using your hands, gently bring the dough together and press it into a ½-inch-thick round (it should be 8-inches in diameter). You want the dough to hold together, but you don’t want to overwork it. Using a sharp knife or bench scraper, cut the dough into 8 triangles (make sure you cut all the way through, but you don’t need to separate the triangles).
Brush the top of the scones lightly with the egg wash (you won’t need it all). Sprinkle with the sliced almonds. Bake until golden brown, about 22-25 minutes. Transfer the pan to a rack and let cool 5 minutes. Using a sharp knife or bench scraper, separate the triangles into individual scones.