Start from what the observer has to see. Choose a position with a clear view of the feature you are demonstrating, keep the observer outside the rod and fly path, and make sure neither of you is looking into the sun.

For a loop demonstration, beside you and slightly behind — on your non-casting-arm side, clear of the rod plane — usually gives that view. Directly behind you the cast is nearly edge-on: the loop collapses into a line, and the width and the shape of the fly leg are lost, which is the point of the demonstration. From the side, the nose, both legs and the loop shape are visible at once. Treat that as a position for this demonstration, not a rule for every task: move to wherever the feature is visible and the observer is out of the way.

Check the light too. Glare is what to avoid: the observer should not have to look into the sun, and the line should read against a plain background, because dark trees and bright sky both swallow a fly line. If the light is wrong, move both of you, not just the observer.

The guide gives no fixed position; it gives the test the position has to pass. A demonstration has to be easy to see, and the style must be something the student can understand, repeat and retain.

Source

The CI Study Guide (2025) (PDF) does not prescribe a position; this answer follows from its demonstration and course-setting guidance. Terms from the FFI Fly Casting Definitions.