Create a Clonezilla bootable USB flash drive

Use your favorite search engine to search for "Clonezilla" and choose the official website.

Choose the "Ubuntu-based alternative stable" version.

Make sure the CPU archictecture is "amd64" and the file type is "iso". Click "Download".

The file will be downloaded to the "Downloads" folder.

Create a directory "ISO" and move the file into that directory.