Preheat the oven to 350 degrees F (175 degrees C). Grease an 8-inch square baking dish.

Stir cocoa powder and coconut oil together in a saucepan over low heat until coconut oil has melted, about 5 minutes. Remove from the heat and let cool, about 5 minutes.

Beat sugar, eggs, salt, and vanilla in a bowl with an electric mixer. Stir in cooled cocoa mixture, then whisk in coconut flour until no lumps remain. Pour batter into the prepared baking dish and sprinkle chocolate chips over top.

Bake in the preheated oven until a toothpick inserted into the center comes out clean, about 35 minutes.