In blender, combine all ingredients except melted coconut oil and blend to a smooth cream of even consistency. This can take several minutes. If needed, add 1-2 Tbsp more water. While blender is running, incorporate melted coconut oil.
Place mixture in a pastry bag with a narrow nozzle.
Trace a spiral of frosting on the pie from the center to the rim of the pie plate. With a chopstick, trace a dozen lines in the frosting at regular intervals from the center to the rim to resemble a spider web.