The first step is the create a relief using the bevel tool, but we'll do it with a twist. That is to use the limit to height tool which effectively flattens the top with a nice bevel around the edge.
The gun mount relief were then combined with the turret reliefs.
The two halves of the turret then got a round modification by using the ADD TO RELIEF command using the two circles as masks. These reliefs were created separately and then merged highest with their respective halves of the turret. The large circle is the top portion. We'll build a hatch onto it shortly.
That's all I can fit on this post but next time we'll build the final bits to get this ready for routing.