There appear to be two ways of teaching this in the UK. The RAF way which is fairly consistent between instructors and the non-military way where the instructor frequently expects the student to learn the whole exercise in one go.
Prior to Ex 16 the candidate has learned to glide the aircraft to the ground from either downwind or base leg. I personally like the European method of 2000ft above the field as it is more adaptable.
Start the exercise by revising the glide; then after looking at fields from different heights to assess aspect and determine what can and can't be seen, demonstrate the complete package without involving the student.
The teaching begins with the next chunk, from engine failure to the skill they already have, the glide to land. Until the student can join these two events together there is no point doing anything else. Initially, you can use selected fields so that field selection becomes another skill.
Slowly work the student up to the full procedure, but only after they have demonstrated they can combine the varous skills.