If you have a raw .app folder and need to package it cleanly into a new IPA file from scratch, the command line offers the most reliable, error-free results. On macOS / Linux Terminal:
Even after converting a ZIP to IPA, the file will install on a non-jailbroken iOS device unless it is properly signed with a valid developer certificate or distribution profile. convert zip to ipa new
For a more visual approach, if you are on a Mac: If you have a raw