Documentation needed: decoding just one file

We repeatedly get questions in the forum about how to decode just one file.
It would be good if we had a documentation page or sub-page about this, that would describe the various steps required to do this, in the context of one of the example scripts.

Review the existing documentation and example scripts first, then use the recurring forum questions as context for the missing guidance. Add a documentation page or sub-page that explains the steps for decoding one file using one example script; done means a newcomer can follow those steps without needing forum help.

Written by the indexing model from the issue text.