TinkerCAD is a free, web-based platform designed to provide a starting point for those wanting to learn 3D modeling. It exposes the basic tools of 3D modeling, constructing a model out of simpler shapes by joining the two or using one to create a hole in the other. Despite its simplicity, TinkerCAD allows users to create elaborately detailed models, and it gives users a solid base to learn more advanced platforms like Fusion 360 or Blender.
1. Open TinkerCAD at https://www.tinkercad.com/.