Simplify3D User Forum

Hi, new user here. I am making a part with a flat, horizontal, downward facing ledge. It is not getting a solid surface (everywhere else is); I can see the infill. I read about the top and bottom layers. Does bottom layer apply to other bottom layers that are not on the base? I suspect not. But then how do I get this to fill as a solid? Thanks

I should mention that this is only about a 2mm wide shoulder, no support.