Hello,
There's no method to create a WordFragment from a DOCX. But you can merge a DOCX and then use DOCXPath to move it to any position of the document.
On https://www.phpdocx.com/documentation/cookbook/merge-docx-documents-anywhere you can find a recipe that explains how to do it.
Premium licenses can do this using in-memory documents but Advanced licenses need to use documents in the file system.
Regards.