Hello I have this Cube and it has two skew side but I have no Idea to get a
third shew and the forth should be in a perfect 90 degree angle.
My code so far.

$fn=200;
Radius = 10;
dRadius = 2 * Radius;

Length = 45 - dRadius;
WidthD = 75 - dRadius;

Width  =  WidthD - dRadius * 2;
Height = 75;

cornerRadius = 10;

inRedBox(0,0,0);
//inRedBox(0,50,0);

module inRedBox(x,y,z)
{
union() {
translate([x, y, z]){
difference() {
squerefunel(Length, WidthD , Height);
translate([3,-3,3]) squerefunel(Length - 6, WidthD - 6 , Height +100);
} }
} }

module squerefunel(x, y, z ) {

Skew1 = 5;
Skew2 = 10;

//translate([x + 140 , - y - Radius , 0]) cube ([ dRadius ,  y + dRadius,
z]);

minkowski(){
  rotate([90,0,0]) linear_extrude(height = x )
polygon(points=[[0,0],[-Skew1, z],[y+Skew2, z],[y  , 0]]); 
  translate([ Width-dRadius,-Radius,0]) {
     cylinder(r=Radius, h=0.01);     
}      }   }

--
Sent from: http://forum.openscad.org/

I got it by myself. I thought I hate this polyhedron lets give it a chance
https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Primitive_Solids#polyhedron
this make it real easy to understand
so that is my code

$fn=200;

Radius = 10;
dRadius = 2 * Radius;

Length = 45 - dRadius;
WidthD = 75 - dRadius;

Width  =  WidthD - dRadius * 2;
Height = 75;

cornerRadius = 10;

inRedBox(0,0,0);
// inRedBox(0,50,0);

CubeFaces = [
[0,1,2,3],  // bottom
[4,5,1,0],  // front
[7,6,5,4],  // top
[5,6,2,1],  // right
[6,7,3,2],  // back
[7,4,0,3]]; // left

module inRedBox(x,y,z)
{
union() {
translate([x, y, z]){
difference() {
squerefunel(Length, WidthD , Height);
translate([3,3,3]) squerefunel(Length - 6, WidthD - 6 , Height +100);
} }
} }

module squerefunel(x, y, z ) {
CubePoints = [
[ 0 ,  0,  0 ],  //0
[ x ,  0,  0 ],  //1
[ x,  y,  0 ],  //2
[ 0,  y,  0 ],  //3
[-2.5,  0,  z ],  //4
[ x+2.5,  0,  z ],  //5
[ x+2.5,  y+5,  z ],  //6
[-2.5,  y+5,  z ]]; //7

minkowski(){
  polyhedron(CubePoints, CubeFaces);
    cylinder(r=Radius, h=0.01);  

}
}
I think the polyhedron will be pretty helpful in the future

--
Sent from: http://forum.openscad.org/

You could avoid polyhedron and minkowski in your model. Just do a shallow
linear_extrude() of an offseting of a rectangle for each top and bottom
surfaces and hull() them.

--
Sent from: http://forum.openscad.org/