1. Cut a sheet of heavy white cardstock to 8.5 x 11 inches.
  2. Score four vertical column lines spaced 2 inches apart (leaving a 0.5-inch gluing tab at the end).
  3. Score horizontal lines across to divide the carton into a bottom base, main body, creased top roof fold, and top sealing tab.
  4. Draw cute pastel milk labels on the main body panels (e.g., a smiling strawberry or cow face) using fine-liners and pastel markers.
  5. Fold along all score lines, apply double-sided tape to the side tab, and seal the box into a 3D rectangular tube.
  6. Fold in the bottom flaps and glue them flat. Pinch the top side panels inward to form the classic milk carton roof, securing the top ridge with a mini wooden clothespin.