Method and system for automatically forming packaging boxes and packaging an article therein, preferably simultaneously with the formation of said boxes. At least four folding units fold side and end panels of a blank upwardly. The four folding units comprise a front pair of folding units and a rear pair of folding units positioned upstream at a longitudinal distance from the front pair of folding units seen in conveying direction, and the folding units of the front pair and the folding units of the rear pair are positioned at a respective transverse distance from each other. Said longitudinal distance is adjustable during feeding of the custom sized blank into the supporting station, preferably by starting the displacement of the front pair of folding units towards the sealing station earlier than the displacement of the rear pair of folding units.