Instead of drawing every line manually, use the Box Builder (usually a wizard icon).
The Result: ArtiosCAD has just drawn a net (the flat pattern). You see a cross shape. The red lines represent score lines (creases where the box folds), and the black lines represent cut lines (where the knife goes).
We need 40mm walls on all sides.
Even with a great ArtiosCAD tutorial, users make these errors:
Error 1: The "Overcut"
Error 2: Board Wrap (The Gap)
Error 3: Missing Bridges
Go to File > Save As. Save it as an .ARD (ArtiosCAD Design) file. This preserves the parametric data.