My current best method is to use my (Android) phone with the "Chessvision" app. It's free (probably because it's an low-low-key ad for their web site that processes entire books in PDF) .
Only tedious part is sending it to the PC -- not serious, and my method is "Share" to "Discord" on a #channel I use specifically for these -- then copy on the PC Discord app easily.
Hi, Chessvision.ai creator here - glad you like the app. For sending diagrams to your PC there is another method you can try. In the app, there is this Diagram Library that you can access from the Menu in the top-right corner. It contains all the diagrams you scanned and marked with the Star (there is a Star button just above the Analysis Board and clicking it adds the diagram to the Library). Then, on PC, open https://my.chessvision.ai in your browser, log in with the same account you use for the mobile app, and go to the Diagram Library tab which is synced to your Library in the mobile app - you can easily export/copy diagrams you want from there. If you have any questions feel free to email me
How to make puzzles if you have a FEN
Click here