How to connect Phoenix to my Core

Currently i’m half way done my core. At the moment I am trying to connect my core to phoenix, and I have the following questions:

1. Do I create a “Poncho” project in which the phoenix project resides inside of my core project, see project structure below.
   MyAppCore
   -lib
   -phoenix
   -lib

2. In chapter 9 the following is stated

“If you want to use a simple mix project as a dependency, whether it’s an OTP project or a simple library, you don’t care about the callback structure. Sometimes, though, you’ll want to replace the boundary layer in Chapter 6, Isolate Process Machinery in a Boundary with one wired directly to the framework you’re using. ”

Does that mean I can replace the boundary layer step in my core with phoenix?