you want a ditched margin on your solid model then? straightforward enough, few options. in your model builder you can choose to create a model with no dies, however to get the ditching, i am confident in saying you can either simply select unsectioned model in the order form, or manually sculpt around the margin with the Minus tool if you are also working not on crowns and copings but temps (for which 3shape will not demand a die cut out)