To achieve this box I used the cardboard Bristol. The purple square to the cover is 40 cm, the base is purple instead of 37 cm .
1 - fold along the two diagonals
2 - fold the corners with the center making coicidere
3 - fold in half parallel to the sides
4 - fold the square diagonally to form a fold internal
5 - fold two opposite corners
6 - the other two fold creases in incorporating internal
7 - et voila , the box is finished!
The same procedure applies to the base. To get a box higher to paste strips of cardboard 14 x 10 cm on the walls of the base.
And here is the finished box :
