This might be the way we clone a sheet
Using importContent
The best way is to analyse the bfore and after.
unpack the original template
compare with the unpacked new (new1)
use the new as a template (new1) to make new2
compare new1 with new2
# create the unpacked folders
unzip -d orig original_file.pptx
unzip -d new new_file.pptx
mkdir old-new-compare
find old-new-compare/
find new -type f | xargs -L1 -Ixx sh -c 'cp xx old-new-compare/$(echo xx | sed "s/\//_/g")'
find orig -type f | xargs -L1 -Ixx sh -c 'cp xx old-new-compare/$(echo xx | sed "s/\//_/g")'
find old-new-compare -type f -name '*.xml' | xargs -L1 -Ixx sh -c 'mv xx xx.bak && xmllint --format xx.bak -o xx'
Some hints but no answers
http://apache-poi.1045710.n5.nabble.com/XSLF-copy-slides-td5147500.html