How to Make It
Heat oven to 375° F. In a medium bowl, toss together the blueberries, lemon juice, ¼ cup of the granulated sugar, and 3 tablespoons of the flour. Transfer to a shallow 2-quart baking dish.
In a medium bowl, toss together the brown sugar, the remaining ¾ cup flour, the remaining ¼ cup granulated sugar, and the salt. Using your hands or a pastry blender, work the butter into the flour mixture until coarse crumbs form. Add the almonds and oats and toss to combine. Scatter over the blueberries.
Place the baking dish on a foil-lined rimmed baking sheet and bake until the topping is brown and the filling is bubbling all over (not just around the edges), 50 to 60 minutes. Tent with foil if browning too quickly. Let cool at least 15 minutes before serving with vanilla ice cream.