Alright guys and gals, I fixed it!
Did it the whole way round, even the bottom. d 
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I used the same method of going round the entire cube selecting faces then flipping normals a few at a time. I found the ones at the bottom too 
It’s a simple matter of making sure you first have back-faces culled. Next you change to edit mode, with selection stuck to faces. I then right-clicked and held down shift to select all invisible faces. Maybe it’s not “proper” as showing the normals explicitly, but it works.
I did it by selecting faces one by one in edit mode, is there another way to do this?? 
