Preheat the oven to 350°F (175°C).
Grease a 8x4-inch loaf pan lightly with coconut oil, and line it with parchment paper so that the paper is hanging over the sides of the pan.
In a medium mixing bowl, whisk together the cocoa and boiling water until smooth.
Allow to cool to room temperature, then slowly whisk in vanilla, flaxseed, orange juice and maple syrup.
In a large mixing bowl, combine flour, baking powder, salt and orange zest.
Add half of the chocolate mixture and coconut oil to the flour mixture. Mix on low with a handheld or a stand mixer until the dry ingredients are moistened. Scrape down the sides.
Gradually add in the remaining chocolate mixture in two batches, mixing with a spatula.
Scrape the batter into the prepared pan and smooth the surface with a spatula. Sprinkle the top with chocolate chips. This is optional, but highly recommended.
Bake for 50 minutes or until a toothpick inserted in the centre comes out clean.
Let the cake cool in the pan on a wire rack for 10 minutes. Then, gently lift the cake out of the pan using the edges of the parchment paper and transfer onto the wire rack. Reinvert it so that the top is up, and cool completely before slicing it.
This cake is best when served at room temperature.