If you turn of internet connection for example, generate your addresses and then uninstall electrum.
that doesn't do anything except giving you a
false sense of security.
for example you could have been a victim of a phishing attack and have a malicious software pretending to be Electrum. installing that then turning of internet connection will result in generating the same malicious wallet and losing your coins all the same.
the correct way has been said many times already so here is a summary the mandatory steps:
1. finding and downloading the correct source code (to compile on your own) or finding the correct developer's PGP public key utilizing
Web of trust.
2. downloading the source code or the compiled binary depending on which route you chose in step 1
3. going on a
clean and air-gap computer (usually through a live Linux).
4. depending on step 1&2 (if the compiled version was downloaded instead of source) verifying the signature with the pubkey
5. installing the wallet and generating the key(s) and creating backups.
