Game Development Reference
3. Reverse the face so that the white (front) face is towards the inside.
4. Import the background image as a texture, and click on the botom let corner of
one of the sides. Then, click on the other edge as you can see in the previous image.
5. Sample the texture and paste on all three other faces.
6. Find an interesing large scale texture and past it onto the botom face.
Select all four top edges and move them up or down to get the full height of the
You might have something like this. Save it and export to Unity: