Creating 'glue' between two parts

I have an assembly which consists of two parts, I want to create a third part to represent 'glue' between the two parts. The space between the parts is open.

One part could be thought of as a sphere (but it isn't - it is a biological shape) with an L shape cut out of it (but not at 90 degrees).  The second part is sort of like a block with a jutting out piece underneath.  This fits into the L.  See pictures attached.  The space between the two parts should be constant.

What is the easiest way that I can do this is SolidWorks? 

I'm really struggling so any help with this would be really appreciated.

Thanks!

El

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