Operation with sublists

Hi everyone!
I have 4 lists, each one with a couple of sublists
Sublists|310x385

How can I join the sublists, obtaining 8 lists, removing the 4 initial lists?
Like in this scheme.

It shouldn’t be so difficult, but I can’t find a right way.
If someone can help me I would be grateful!!

I think, Are you looking for this type of solution.

Regards
Sagar Jain

I think that my case is a little more complicated, because I have to keep the structure of the sublists.
Basically I’d like to know if it’s possible to remove the 4 lists keeping the related sublists to create a new list

Ok I solved, I simply tried with a flatten on the level 3.
solved