Providing to-be-compiled programs in a custom ISO

Hello, I wanted to include a program (Fluxion) in my custom Kali build (I'm trying to build my ISO on a x64 Kali VM with XFCE) but the problem is it doesn't have any .deb file to use, since it must be compiled every time I install it. My question is: how do I include it in a custom ISO?
I tried following this page, because the one you refer to in the "Live build a Custom Kali ISO" thread doesn't exist anymore.
In the 0x03 section it creates this chroot file which supposedly gets fired up at the end of the installation, but I cannot really get if it will be run only once at the end of the installation or it will also be run everytime I run the live environment.
Also, since compiling the app everytime the live environment starts wouldn't be that good of a solution, what's the best way to actually include such a program in a custom ISO?

It's my first time creating a custom ISO, please be gentle :p
Every help is appreciated, thanks in advance.