The unassembled puzzle pieces of a two-sided puzzle are stored in a right-triangular box to form a two-sided puzzle and box assembly. A representation of the image on one side of the two-sided puzzle when assembled is on one triangle-leg first side wall. And a representation of the image on the other side of the puzzle is on the triangle-leg second side wall. Thus, the person assembling the puzzle opens the box, dumps the puzzle pieces out and sets the box up generally with the right angle of the box facing her. She can easily then see both image representations by only moving her head slightly as she puts the puzzle together. She may then figure out which up-or-down way to flip the pieces, as she puts the puzzle together. The puzzle assembly method is also disclosed.