Generate the signed certificate (CRT) file using
the private key and CSR file:
openssl x509 -in mycsrname.csr -out mycrtname.crt -req -signkey mykeyname.key -days 10000

Generate the .pfx file using the private key and
CRT file:
openssl pkcs12 -export -out CERTIFICATE.pfx -inkey mykeyname.key -in mycrtname.crt

Install the .pfx certificate first on the local machine
in Certificate store as
Trusted Root Certification Authorities
before installing the app.

Building your own zip file for Windows

The Flutter executable, .exe, can be found in your
project under build\windows\runner\<build mode>\.
In addition to that executable, you need the following:

From the same directory:
    
      all the .dll files
      the data directory