Bind payload with other apps and make it fully undetectable

How to bind a payload generated by a RAT ( for example: spynote) to any other apk file using apkeasytool in windows ? And how to make the file fully undetectable? (after signing the google play protect get bypassed but a warning pop up mostly in MI phones when I try to install the payload in phone)

I have searched in previous thread but none of the tut works. Help me!

Thanks in advance

It shows high risk warning remove trojan. I am unable to understand why that occurs. HELP