FreeCAD for 3D Printing
3D Printing Design Workbench in FreeCAD could be a bare bones interface that helps novices use FreeCAD. It is preconfigured to get straight into design work - not into setup. The point of a good user interface is that all the setup is done for you - and you can go deeper if you like - but going deeper is not required at startup.
As such, a 3D Printing Design workbench would be a high value - to build on a truly open source solution.
- TLDR FreeCAD - https://www.youtube.com/watch?v=EaHuY6Dcomo