Hi Mala, it looks like the separate surfaces problem is caused because your dome shape was an open surface instead of a closed solid when you did the boolean on it.

You should make the dome into a closed solid before doing the boolean. You can do that by selecting it and running the "Construct > Planar" command which will close off the bottom with a planar surface.

Additionally the cutting objects have a little gap in the middle area, they are also not solids. I closed those up by creating some lofts and joining those in.

- Michael

Hi Mala, in the attached model I've fixed those problems.

So you should be able to open up the attached version, select these 22 edges:



Note don't forget this little one here:



Then you can apply a fillet:



It is helpful to refer to the "object type indicator" here to know if your
selected object is a finished solid or an open surface:



- Michael

Hi Michael, thanks for eliminating the design flaws! I learned from them, replicated them in the design, and also added it to my personal MOI wiki.
Best Mala...