Preheat oven to 350 degrees. Line 8x8-inch square baking dish with parchment paper or spray with nonstick cooking spray.
In medium bowl, whisk together flour blend, almond flour, baking powder and salt. Set aside.
Melt chocolate chips. Pour into large mixing bowl, along with oil and cocoa powder. Stir until smooth.
Add sugar, maple syrup, warm water and vanilla to chocolate mixture. Mix well. Add flour mixture and stir until dough is combined.
Stir 3/4 cup walnuts into brownie dough. Scoop into prepared baking dish. Smooth out with rubber spatula. Sprinkle reserved 1/4 cup walnuts on top and press into dough.
Bake brownies 30-32 minutes. Cool in pan on cooling rack to cool completely. Slice and serve.
Recipe by Sarah Bakes Gluten Free at https://www.sarahbakesgfree.com/2018/02/gluten-free-vegan-walnut-brownies.html