CAD FreeCAD Designer

I am looking for a CAD FreeCAD Designer to design a single part for me. The final design must be in FreeCAD format. I have detailed specifications specifically for sheet metal workers. I am looking for a drawing that I can take to a sheet metal worker and have them print aluminium sheets for me. I want to be able to make up rectangular boxes so the drawings must reflect the fold areas. See picture example of fold area and printed sheet. I must also be able to adjust the sizes on FreeCAD whenever I feel the need.