Navigate to Start Menu > System Tools > Startup Disk Creator
Verify that the Source ISO and Destination Device are correct > click Make Startup Disk
Input the system administrator or root password > wait for the progress bar to display completion
If there are no errors, this finishing screen should display > click OK
Although the prompt is intended to instruct the user to install Ubuntu on the host device, the correct interpretation would be to ignore that advise by unplugging the USB storage (gracefully) from the computer. This thumb drive would then be ready to insert into any target system to install the OS image that it contains.