Preheat oven to 350 degrees Fahrenheit (175 degrees Celsius).
In a small container, whisk together the ground flaxseed meal and warm water; allow to hydrate for 10 minutes to form a thick gel.
In a large mixing bowl, combine the flax gel, maple syrup, brown sugar, melted coconut oil, cornstarch, vanilla extract, and salt; whisk vigorously until the cornstarch is fully incorporated and no lumps remain.
Fold the pecan halves into the liquid mixture until evenly coated.
Pour the filling into the prepared vegan pie crust, ensuring pecans are distributed in an even layer.
Bake on the center rack for 45 to 50 minutes, or until the edges are set and the center has a slight wobble.
Remove from oven and place on a wire cooling rack; the pie must cool completely for at least 4 hours at room temperature to allow the starch structure to set before slicing.