This a great little puzzle by Mineyuki Uyematsu that I saw on Puzzle Will Be Played last week.
http://puzzlewillbeplayed.com/444/CubeLibre/
It's another great example of a printable puzzle that requires no support on RepRap printers.
These 10 puzzle pieces can make both an 8x8 square and a 4x4x4 cube.
I designed a special box in Tinkercad that allows the puzzler to play both games. https://tinkercad.com/things/8Jzfov4OYUA