Steps

1. Download Handbrake (x64 Portable)
2. https://handbrake.fr/downloads.php
3. Add the desired file
4. You can drag and drop it, or via the internal menu, in both cases, it will load it to obtain its information (see quality, ratio, encoding, etc.)
5. /!\ Remember to update the output folder in the software settings!
6. The options
7. > The basic settings are already really good, but I recommend the following adjustments:
8. Format: MKV
9. Video Codec: H.265 (x265)
10. > You can also increase the number of images proposed for the cover image in the software settings (from 10 to 20 for more choices)
11. /!\ Remember to save your profile so you don't have to do it all over again!
12. The waiting line
13. If you only have one file, then you don't need to add it to the list, so you can do "Play" right away
14. If you want to make several files, then you will have to add them one by one to your list, using the "Add to Queue" button, so that it will do them in order when you do "Play"
15. Plex / Roku
16. There is a special preset in the "Devices" menu which is optimized for these media players
17. > It depends on the CPU used for your Plex server, if it is powerful enough, this point will not be vital