Adding or extracting single files from a solid archive takes much longer because the entire archive must be processed.
Optional: Select a "Best" compression method for higher compression. Click OK to generate the solid archive. Key Considerations for Solid Archives: Linsh.rar
If you provide this info, I can tell you if you should be using the rar command-line tool or if a simple right-click in Windows will do the trick. rar - ArchWiki Adding or extracting single files from a solid