Preheat your oven to 300 degrees F. Spray three 8-inch round cake pans with nonstick spray, line the bottoms with parchment paper and spray again. Set aside.
Combine the flour, sugar, cocoa powder, and salt in the bowl of a stand mixer fitted with the paddle attachment and paddle on low speed until mixed.
Add the butter and mix on low speed until the mixture starts to come together in small clusters.
Spread 8 ounces of the chocolate crumbs on the parchment in each the three 8-inch cake pans. Using the back of a spoon, push the crumbs together to form a crust. Bake for 6 to 8 minutes.
Let the crust cool a bit while you make the cake.