How to reverse normals of thick box I am trying to create a box or room that has a slight thickness to the walls, with normals reversed on everything so you can always view the inside from the outside(with backface culling checked)

I have tried adding the solidify modifier to a box, then reversing the normals, but this doesn't work as expected. I then messed around with flipping normals manually by selecting the faces I want the normals flipped on, but this also didnt work.
What other method is there?
Thanks
Check "Only Rim" within the solidify modifier. Make sure you also have "Flip normals" checked within the modifier as well.