I have worked as 3D cad modeller and designer for reputed MNC companies, and also currently working on a business of my own. and I do this work as design is my passion, I can provide the output with best quality and accuracy.
I will first collect all the required inputs, shapes, sizes and materials, and how much area it should cover.
Then i would create 3D models and have your approval if youre okay with the designs or will update if any corrections are required.
then i would go with creating drawings with all the dimensions and Bill of materials to create the product.