Preheat oven to 375 degrees.place large size (14 x 20") oven cooking bag on large cookie sheet.in large bowl,coat blueberries with 3 tablespoons flour.roll out pastry for bottom crust,fit into pan;sprinkle with 1 tablespoon sugar and remaining flour.
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Pour in blueberries;sprinkle with lemon juice and remaining sugar.dot with butter.add lattice top crust made with remaining pastry;slide pie into bag.close bag with nylon tie;make 6 half-inch slits in top.bake 1 hour or until syrup boils and crust is brown
