System for producing a heat insulating layer on a flat roof, wherein the heat insulating layer has a planar base surface facing the flat roof and a planar cover surface remote from the flat roof, said cover surface being inclined in relation to the base surface by an angle of inclination α, wherein the heat insulating layer comprises at least two regions, which each adjoin one another along a hip or a valley, and wherein the slope directions of the cover surfaces of adjoining regions are oriented perpendicularly to one another, comprising - a plurality of series (1, 2, 3), each with a plurality of identical sloped plates made of an insulating material, wherein the sloped plates have planar, square base surfaces and cover surfaces as well as side surfaces (16, 18) perpendicular to the base surface, wherein the cover surface is inclined in relation to the base surface by the angle of inclination α, wherein two parallel side surfaces (16, 18) perpendicular to the slope direction have a starting height and an ending height, respectively, the height difference of which is ΔH, and wherein the sloped plates of all series (1, 2, 3) have the same dimensions of the base and cover surfaces (12, 14), while the heights of the different series (1, 2, 3) differ in such a way that the end height of a preceding series (1, 2) of sloped plates corresponds to the starting height of a subsequent series (2, 3) of sloped plates, but the height difference ΔH in the sloped plates of all series (1, 2, 3) is the same, characterized in that the system further comprises: - a plurality of identical valley compensation plates (20, K), wherein the valley compensation plates (20, K) have planar base surfaces and cover surfaces in the form of a right isosceles triangle, wherein the length of the legs of the triangle correspond substantially to the side length of the base surfaces of the sloped plates, and wherein the valley compensation plates (20, K) have a height of ΔH at the intersection of the legs and has a smaller height of 0 to 2 cm along the hypotenuse; and - a plurality of first identical hip compensation plates (30, G1) and a plurality of second identical hip compensation plates (40, G2), wherein all hip compensation plates (30, G1; 40, G2) have planar base surfaces (32; 42) and cover surfaces (34; 44) in the form of a right isosceles triangle, or, in the case of the second hip compensation plates (40, G2), optionally of an isosceles trapezoid, in which the right-angled tip of the triangle is cut off, wherein the length of the legs of the triangle corresponds substantially to the side length of the base surfaces of the sloped plates, wherein the first hip compensation plates (30, G1) have a constant height of ΔH, and wherein the second hip compensation plates (40, G2) have a height of ΔH along the hypotenuse and a smaller height of 0 to 2 cm at the intersection of the legs or opposite the hypotenuse. - a plurality of series (1, 2, 3), each with a plurality of identical sloped plates made of an insulating material, wherein the sloped plates have planar, square base surfaces and cover surfaces as well as side surfaces (16, 18) perpendicular to the base surface, wherein the cover surface is inclined in relation to the base surface by the angle of inclination α, wherein two parallel side surfaces (16, 18) perpendicular to the slope direction have a starting height and an ending height, respectively, the height difference of which is ΔH, and wherein the sloped plates of all series (1, 2, 3) have the same dimensions of the base and cover surfaces (12, 14), while the heights of the different series (1, 2, 3) differ in such a way that the end height of a preceding series (1, 2) of sloped plates corresponds to the starting height of a subsequent series (2, 3) of sloped plates, but the height difference ΔH in the sloped plates of all series (1, 2, 3) is the same, - a plurality of identical valley compensation plates (20, K), wherein the valley compensation plates (20, K) have planar base surfaces and cover surfaces in the form of a right isosceles triangle, wherein the length of the legs of the triangle correspond substantially to the side length of the base surfaces of the sloped plates, and wherein the valley compensation plates (20, K) have a height of ΔH at the intersection of the legs and has a smaller height of 0 to 2 cm along the hypotenuse; and - a plurality of first identical hip compensation plates (30, G1) and a plurality of second identical hip compensation plates (40, G2), wherein all hip compensation plates (30, G1; 40, G2) have planar base surfaces (32; 42) and cover surfaces (34; 44) in the form of a right isosceles triangle, or, in the case of the second hip compensation plates (40, G2), optionally of an isosceles trapezoid, in which the right-angled tip of the triangle is cut off, wherein the length of the legs of the triangle corresponds substantially to the side length of the base surfaces of the sloped plates, wherein the first hip compensation plates (30, G1) have a constant height of ΔH, and wherein the second hip compensation plates (40, G2) have a height of ΔH along the hypotenuse and a smaller height of 0 to 2 cm at the intersection of the legs or opposite the hypotenuse.