Preheat the oven to 350°F. Line the bottom and sides of a 13- x 9-inch pan with aluminum foil, allowing 2 to 3 inches to extend over the sides; lightly grease foil with cooking spray.

Pulse flour, granulated sugar, and salt in a food processor until combined. Add butter cubes, and pulse until the mixture is crumbly. Reserve 1 cup flour mixture. Press the remaining flour mixture onto the bottom of the prepared pan.

Bake 25 to 30 minutes, until lightly browned. Spread blueberry pie filling over crust in pan. Toss together the reserved flour mixture and almonds. Sprinkle mixture evenly over the filling.

Bake until golden brown for about 40 to 45 minutes and filling is bubbly. Cool completely in pan on a wire rack, about 1 hour. Lift baked bars from pan, using foil sides as handles.

Whisk together powdered sugar and 4 teaspoons lemon juice. Add additional lemon juice, if needed, to reach desired consistency. Drizzle over pecan mixture. Cut into bars.