Method for arranging a top seal foil on a cardboard tray, which method comprises the steps of: - providing a top sealer (22, 23); - providing a cardboard tray folded from an unfolded sheet (1; 30; 50) of cardboard, which tray comprises: - a bottom wall (2; 51) with a circumferential edge composed out of an even number of straight edges (3; 52); - wall parts (4; 53, 54) each arranged to a straight edge (3; 52) of the bottom wall (2; 51); - first flange parts alternately arranged to subsequent wall parts along the circumferential edge, which first flange parts are arranged to an edge of said wall part (4; 54) opposite of, and preferably parallel to, the respective straight edge (3; 52) of the bottom wall (2; 51); wherein the first flange parts comprise at least a first (8; 56), a second (9; 57), and a third (10; 58) elongate flange part section, which are connected parallel and along an elongate edge to each other, wherein the first elongate flange part section (8; 56) is arranged to a respective wall part (4; 53), wherein the third elongate flange part section (10; 58) is connected parallel and along an elongate edge to the second elongate flange part section (9; 57), and wherein the third elongate flange part section (10; 58) is adhered to the outside of the respective wall part (4; 53) wherein the second flange part section (9; 57) is double folded against the first flange part section (10; 58), and wherein the first elongate flange part section (8; 56) slopes downwards towards an outer edge of a respective first flange part, and is sloping downwards towards the second elongate flange part section (9; 57); - arranging the cardboard tray in the top sealer (22, 23) such that the first elongate flange part section (8;56) is pressed to an horizontal position; - providing a top seal foil over the cardboard tray; - sealing the top seal foil to the flange parts. - providing a top sealer (22, 23); - providing a cardboard tray folded from an unfolded sheet (1; 30; 50) of cardboard, which tray comprises: - a bottom wall (2; 51) with a circumferential edge composed out of an even number of straight edges (3; 52); - wall parts (4; 53, 54) each arranged to a straight edge (3; 52) of the bottom wall (2; 51); - first flange parts alternately arranged to subsequent wall parts along the circumferential edge, which first flange parts are arranged to an edge of said wall part (4; 54) opposite of, and preferably parallel to, the respective straight edge (3; 52) of the bottom wall (2; 51); wherein the first flange parts comprise at least a first (8; 56), a second (9; 57), and a third (10; 58) elongate flange part section, which are connected parallel and along an elongate edge to each other, wherein the first elongate flange part section (8; 56) is arranged to a respective wall part (4; 53), wherein the third elongate flange part section (10; 58) is connected parallel and along an elongate edge to the second elongate flange part section (9; 57), and wherein the third elongate flange part section (10; 58) is adhered to the outside of the respective wall part (4; 53) wherein the second flange part section (9; 57) is double folded against the first flange part section (10; 58), and wherein the first elongate flange part section (8; 56) slopes downwards towards an outer edge of a respective first flange part, and is sloping downwards towards the second elongate flange part section (9; 57); wherein the first flange parts comprise at least a first (8; 56), a second (9; 57), and a third (10; 58) elongate flange part section, which are connected parallel and along an elongate edge to each other, wherein the first elongate flange part section (8; 56) is arranged to a respective wall part (4; 53), wherein the third elongate flange part section (10; 58) is connected parallel and along an elongate edge to the second elongate flange part section (9; 57), and wherein the third elongate flange part section (10; 58) is adhered to the outside of the respective wall part (4; 53) wherein the second flange part section (9; 57) is double folded against the first flange part section (10; 58), and wherein the first elongate flange part section (8; 56) slopes downwards towards an outer edge of a respective first flange part, and is sloping downwards towards the second elongate flange part section (9; 57); - arranging the cardboard tray in the top sealer (22, 23) such that the first elongate flange part section (8;56) is pressed to an horizontal position; - providing a top seal foil over the cardboard tray; - sealing the top seal foil to the flange parts.