manually sign my flutter app in release mode

Request details I have an app that is completely finished. Every time that I try to upload the app to the Play Store, the Play Store tells me that the app has been signed in debugging mode. When I try to follow tutorials to help me sign it in release mode, Android Studio either shows options that aren't available for me or I have already done what they've said yet the app still hasn't been signed in release mode. I have tried to figure out if there is a manual way to sign the app in release mode but this is all very confusing to me as I am a beginner with coding. I haven't worked on this project in a very long time but I would love to just get this signed correctly. My only goal is to get the app signed in release mode. Thank you.