Copy specific slices from existing segments to single Binary Map

Hi, sorry I was quite convoluted in my initial question.

I got to the part where I combined two segments into one as seen below:

But what I would like to do is find a way to automate a method in “filling the gap” between the seperate segments. I thought of using the “fill in between slices” method, but that requires actually using paint to paint on two different slices to fill in the gap, which is not automatic. Is there any way to do this automatically?