Preheat oven to 200 degrees Celsius.
In a food processor, combine the flour, sugar, and salt and pulse until combined. Then slowly add the margarine, coconut oil pulsing all the while, until you get a coarse meal. Then slowly add the ice water, 1 tbsp at the time, and pulse until a dough ball forms.
Turn your dough out onto a floured surface into 2 equal sized balls. Flatten into disks, wrap in wax paper and pop in the fridge for at least 30 minutes.
Roll the first disk of dough into a large circle, transfer and fit into a 8' pie plate. Spoon the blueberry mixture into the crust, leaving any remaining liquid in the bowl. Roll your second dough into a large circle the same size as your pie. Slice the lattice strips and starting from the center, place the longest strip first, pressing the ends into the crust at the rim. Then do the same thing the opposite way to form a lattice pattern. Decorative edge in desired pattern. Brush pie with coconut oil. Bake for 40-45 minutes until evenly browned and bubbling. Allow it to cool completely.