Get the ISO file from a reputable community forum (like TeamOS or the developer's official YouTube/Patreon).

Even when not malicious, modified ISOs can cause serious issues. One Reddit user shared their experience after downloading a Windows 10 ISO from a website called Windowstan.com—which appeared as a normal free OS repository. After installation, their computer began behaving strangely, and the root cause was traced back to the modified ISO they had installed.

Only from the developer's official Internet Archive page or his verified GitHub (never from random file hosters). Even then, scan it with Windows Defender Offline.