Combine flour, baking soda, salt, sugar, crackers and melted butter in that order. Spread 1/2 of the mixture in a lightly buttered 9" pie plate, Cover with blueberry pie filling which has been mixed with lemon juice, and then top with the remaing soda cracker mix.Bake in preheated 375~F oven for 25-30 minutes. Cool on rack. Serve with lightly sweetened-vanilla flavored whipped cream or with vanilla ice cream. This pie makes its own crust.