Minecraft wiki entry for Curved_roofs, associated text: A cone-shaped roof, as might be seen atop a circular tower or for a church spire, can be constructed in a similar way to the method used for domes. As for domes it's also possible, in principle, to 'smooth' the curve a bit using stairs or slabs, but this is still fiddly and is not recommended except for practiced builders. Recognizable cones are very hard to model except at large scales, or possibly by using Minecraft plugins to tweak the shape of the curve.