From FreeCAD Documentation
- Press the Filling button.
- The Boundaries task panel opens. See Options.
- Select two or more edges in the 3D view:
- There is no need to press the Add edge button in the Boundaries section at this time.
- The edges must be selected in consecutive order.
- The edges must be connected, but the complete boundary need not be closed.
- The complete boundary should not self-intersect.
- For a 360° circular boundary two semicircular edges can be selected.
- A preview of the final shape will be shown once enough valid geometry has been selected.
- Optionally select a Support surface. See Example.
- Optionally select one or more Edge constraints.
- Optionally select one or more Vertex constraints.
- Press OK button.