Fill in between different contoures

Slicer version: 4.10.1
Hi 3D slicer experts and all
I have a number of contours that are in separate segments(like Fig A). I want to make a model of all of them (like Fig B). How can I fill in between them to finally have a contour and make an integrated model(Fig B)?
Thanks a lot

You can use Segment editor for this: choose Scissors effect, Operation → Fill inside; Masking / Editable area → Inside all segments, and trace a large circle around the object. For automated processing the easiest is to threshold the labelmap.