How does Function Declaration Instantiation apply to functions without parameters?

Hello everyone. I've been trying to understand as applied to functions without parameters.

Say I have the function:

function f() {
      const x = 2;
      let y = 3;
      var z = 4;

Is a single Lexical Environment created for x,y,z or is z stored on the first LE and x,y on another one with Outer Environment set to the first LE...or something else I didn't think of?

I'm excluding the VE because there's only 1 reference (20d) and it looks only related to either a strict function or a function with Parameter Expressions, but this function has no parameters at all.

This is closely related to a StackOverflow question (this comment in particular) which unfortunately didn't get the answer needed.