Split a cube into several pieces?

Dear community.

Got a small problem, hopefully theres a ridiculous easy solution to it.

I have a cube that is instantiated to the sceen with its width and height set by the player. Then I want to do this, according to player selection, make the cube into smaller pieces that are equal in size according to initial width and height.

Sort of like this

Have pretty much done all the coding before, and after. But missing a good way of doing this part. These cubes are buttons and therefore its important that they are separated or clickable in each separate area.

Any good ideas or help on this would be greatly appreciated :=)