Lightly mist a 10x8-inch aluminum-foil pan with nonstick cooking spray.

In a nonreactive bowl, combine blueberries, ¼ cup of flour, sugar, lemon juice, and lemon zest, then gently toss to mix. Spoon in blueberry mixture into prepared pan.

Place biscotti crumbles, brown sugar, and remaining ½ cup of flour in a food processor and process until a coarse powder forms. Add butter and salt, then pulse until crumbly. Spoon mixture over blueberries.

Set up the grill for indirect grilling and preheat to medium-high heat. If using a gas grill, place all of the wood chips in the smoker box and run the grill on high until you see smoke, then reduce heat to medium high. If using a charcoal grill, preheat it to medium high, then toss all of the wood chips or chunks on the coals.

Place pan in the center of the hot grate, away from the heat, and cover the grill. Cook for 40 minutes, or until blueberry mixture is bubbling and top is browned. Serve with vanilla ice cream (if using).