Take an old holiday greeting card.
Open the card and cut it on the center fold. Make an X on the left panel.
Fold the top portion of the card panel halfway to the center. Do the same with the bottom portion of the card panel.
Cut notches in the four quadrants, as shown below.
Fold the left and right sides into the card. Tape the tabs to form an open box.
Turn it over. You've made the top of your gift box!
Repeat the same with the other panel of the card.
This will become the bottom part of your gift box.
Fold the top and botton portions of the card, cut the notches in the corners,
fold the sides, and tape the tabs.
Fit the top and bottom together. You might need to trim the sides a bit.