Two cubes, union them in a suitable shape, Choose your sphere of choice (primary, white) and then your cubes (green, ie, secondary) and take Booleans DIFFERENCE.

And there you go. The absolout Quickest way I could think of, no doubt others can do better then me, but I wanted to help.

I included step by step ANIMATED GIF if I am just rambling incoherent here.

Hope that helps.