I want to model corners like this, but I am struggling as corners won't have same wall thickness as you see from side.  can someone help give me a hand? I don't have dimensions but something that looks similar will do?  I really don't know what to do. thanks in advance.  If picture is blurry. I have attached the image link too. 

https://limewire.com/d/OHeMb#M3bxLKfUd2