Preheat oven to 350 degrees F (175 degrees C). Lightly oil a baking dish.
Beat chia meal and both amounts of water together in a bowl; let stand until thick, about 5 minutes. Blend raw sugar and agave into chia seed mixture with high speed blender. Add vegan margarine and vanilla extract; blend.
Mix brown rice flour, almond meal, baking powder, and salt together in a large bowl. Stir cocoa powder into the flour mixture. Add chia meal mixture and stir until combined; pour into prepared baking dish.
Bake in the preheated oven until the top is dry and the edges have started to pull away from the sides of the pan, 45 to 55 minutes.
