With a pencil and a ruler, draw a line along both diagonals, creating an X. If the paper has a right side and a wrong one, draw the lines on the wrong side.
Bring each corner to the center of the X. Crease the folds with a bone folder or the back of a spoon, and then unfold the corners. Each fold creates a new X along the diagonal. Fold each corner to the new X closest to the opposite corner. Crease the folds, and unfold. Fold each corner to the closest X along the diagonal. Crease the folds, and unfold.
The card stock now has a grid of folds. At one corner, make two cuts along the folds on either side of the diagonal that are the length of two squares in the grid. Repeat the cuts at the opposite corner.
Fold the two uncut corners into the center. To create the sides of the box, fold up the next crease on either side. To finish the other two sides, fold the cut ends in towards each other, and fold the two remaining corners into the center of the box. Repeat the above steps with a slightly smaller square of paper for the bottom of the gift box.