Preheat the oven to 375˚F.
Mix flax meal and water; let it sit for 15 minutes to thicken.
Melt vegan butter (preferably on the stove) and add it to a stand mixer with both sugars. Beat on medium speed for 2-3 minutes.
In a separate bowl, whisk together gluten-free flour, oat flour, baking soda, and salt.
Add flax "egg" and vanilla to the butter mixture, mixing until combined.
Incorporate the dry mixture into the wet ingredients in batches. Fold in both types of chocolate.
Using a large cookie dough scoop (2-3 tbsp), arrange scoops on a parchment-paper-lined baking sheet.
Freeze for 15-20 minutes to prevent excessive spreading during baking.
Bake 5-6 cookies at a time for 12 minutes (or 9-10 minutes for smaller cookies).
Optional: After baking, use a fork to press the edges for crinkly, crispy edges. Sprinkle with flaky salt if desired.
Let cookies cool for 10 minutes, then savor the goodness!