Preheat the oven to 350ºF. Grease a 9 X 9 pie dish and line the bottom of the dish with parchment paper, with some sticking out the sides, to make it easier to remove the bars.
To the bowl of a food processor, add the dry ingredients. Process to mix. Then add the water while processing, until a dough starts to come together. You should be able to squeeze it between your fingers and it will hold together, so you may need to add another teaspoonful of water if it's too dry for that.
Dump the crust into the pan and press it into the bottom. Make the layer as even as possible. Bake the crust for 10 minutes.
While the crust is baking, wipe out the bowl of the food processor (or don't, if you are lazy like me and have decided that any leftover crust bits will just get mixed into the bar filling) and put it back on the base. Add the filling ingredients and process until smooth. Allow to set for 5 minutes to give the flax seed time to gel in the liquid.
Stir once more, then pour the filling into the prepared crust and smooth over, if needed, with a spatula or spoon.
Bake the pie for 60 - 65 minutes until the filling jiggles a little in the center.
Remove the pan of bars and let cool for at least 1 hour. Cover the pan, then transfer to the fridge and cool another 4 - 6 hours, for best results, or overnight.
Slice and serve with cinnamon-spiced pecans, coconut yogurt frosting, Halloween decorations and/or a sprinkle of pumpkin pie spice.