There are several option how to remove flowRoots:
replace notempty flow-text using (Inkscape)
- Click on the in Inkscape visible Text or click on the -tag in the XML Editor of Inkscape
- go to
Text
-menu: Click on Convert to Text
(you could also click on Unflow, but this one sometimes replaces the text)
- repeat for all (nonempty) flow-texts
- save file (If you save as a Optimized-SVG you will get a flowRoot-warning if you forgot one text)
There is also an automatic script
inkscape filename.svg --verb=EditSelectAll --verb=ObjectFlowtextToText --verb=FileSave --verb=FileClose --verb=FileQuit
That the black square won't get rendered (Text-Editor)
add fill-opacity="0"
in the < rect … fill-opacity="0"/>
(or in < path d="…" fill-opacity="0">
) which is between < flowRegion>
and < /flowRegion>
Further methods
If it does not work: further methods are explained on Wikimedia