A square creates the primary, and largest, portion of the Box icon. On top of the square is a lid, which is rectangle that extends just beyond the box on both sides and the height is quite short. A narrow, oblong cylinder in the top half of the box creates a handle.
This page shows the different variations of the Box from an Icons8 icon pack. Feel free to resize and recolor the icon, and then download the icon in PNG format for free.