Preheat the oven to 350 degrees(F).
In a large mixing bowl, sift the flour and powdered sugar. Stir in the salt.
Add the vegan butter and vanilla to the bowl and stir with a wooden spoon to combine. Or use a hand mixer. This will be super thick, like a cookie dough. Just continue to stir until fully combined.
Pour half of the dough into the bottom of a 9x9 inch baking dish lined with parchment paper.
Press the dough into the bottom of the pan evenly to form the crust.
Add the oats to the remaining dough stir together and set aside.
Now in a separate large mixing bowl, whisk together the corn syrup, sugar, cornstarch, flour, salt, melted butter and vanilla until fully combined.
Pour the pecans into the bowl, then fold them into the mixture.
Pour the pecan mixture over the crust and smooth out evenly.
Crumble the rest of the dough over the top of the pecan filling evenly.
Bake for 30-35 minutes or until the bars are golden brown.
I recommend letting cool until firm on the counter and then removing the bars from the pan to finish cooling. Especially if using a metal pan. The edges will get really crunchy like toffee and then the bars are hard to remove from the pan if left in the pan to cool.