I converted the STEP file provided by Plamen to an STL file here - https://brax.me/f/Brax3_Model-BraX3%203D%20model%20-%20no%20texture.stl/T4AZ686c3caa315132.58039020
This can be used in programs like FreeCAD to create accessories, cases, etc. The STL file needs to be converted into a shape that can be used and manipulated in FreeCAD. This process is documented online in many places like YT.
For FreeCAD: Simply design your accessory (stand, dock, case, mount, etc.) and then place this model in the spot where the phone would sit. Then select your creation, hold ctrl and then click this model. Then click the “Cut” button in the top right toolbar. This will cut out the exact shape of the phone from your design; giving you a place for the phone to sit inside the design. You may need to slightly adjust margins for some designs. So, keep this in mind; but this should help out a lot.