Floating copper regions can’t be removed automatically yet. You will need to clear them manually:
I recommend using Flux’s PCB editing tools to select and delete each orphan copper area:
- Switch to the PCB editor in 2D view.
- In the DRC panel, click a “Floating Copper” error to zoom to the region.
- Use the selection tool to click on the isolated copper pour or track segment.
- Press Delete.
Repeat until all floating copper errors are cleared, then rerun DRC to confirm.