If you use the constant aspect technique all you need to know is the Low Key height for you particular aircraft. You can find this out by flying a few glide approaches and working out the best point to take the gear. Anyone who flies a single should have an idea at what height they need to be abeam the touchdown point to assure a landing.
Trim for the correct glide speed and maintain the aspect to the touchdownpoint by varying the bank angle in the final turn.
I recall showing the owner of a Piper Lance how to do this. 2500 ft abeam with the gear halfway around the turn worked well.