Advice/Building Technique Needed

I quickly grabbed this screenshot from a fb video, so I apologize for not being able to credit original builder, but does anyone know how they got those wall tiles at 45 degree angles? For the life of me, I can't figure it out using a legal technique (maybe that's what I'm missing though). Anyone have any tips/ideas/recommendations? submitted by /u/thedapperesq [link] [comments]