Making ISO of Big Sur in terminal

Hello,

I've tried several different attempts to complete this task, always with the same result, saying

sudo: /Applications/Install macOS Big Sur/Contents/Resources/createinstallmedia: command not found

after successfully creating the file in /tmp using hdiutil and attaching. I can't see why I have the issue, I've seen the same steps listed on several websites, and I have also set my shell profile to use bash instead of zsh. I thought this might be why I was not permitted to use sudo so I switched. Please any help would be greatly appreciated, I had completed the same process on my other macbook with High Sierra without any issues. Please let me know what, if anything I'm doing wrong. Thank you!