A cardboard tray folded from an unfolded sheet of cardboard includes: a bottom wall with a circumferential edge formed out of an even number of straight edges; wall parts each arranged to a straight edge of the bottom wall; and first flange parts alternately arranged to subsequent wall parts along the circumferential edge. The first flange parts include at least a first, a second, and a third elongate flange part section, which are connected parallel and along an elongate edge to each other. The first elongate flange part section is arranged to the respective wall part, the third elongate flange part section is connected parallel and along an elongate edge to the second elongate flange part section, the third elongate flange part section is adhered to the outside of the respective wall part, and the second flange part section is double folded against the first flange part section.