Most of the replies aren't answering the question ..ie how it is flown and not the cockpit procedures.
It wasn't until I got into glider instruction and alpine flying that I really understood how it should be taught.
The French teach the constant angle...as in constant angle to the aiming point.
This I demonstrated with an approx 20 degree angle from the wing tip.
Patter..bisect the angle between wingtip and vertical...then bisect that..should give 22 1/2 degrees ..but the eyeball/brain flattens that angle naturally.
So you keep the aiming point at that angle to the wing tip.
Secondly the BGA patter talks about detail to judge height...windows frames...telegraph poles..legs on cows..etc.
Thirdly the Zig Zag circuit demonstartion.
Having had more chop flights than any other student who passed their commercial pilots license I know the problems...most instructors don't teach how to judge the perspective.
The other problem in judging the heights is knowing the size of the objects....in ireland the fields are much smaller than in east Anglia..and pine trees in the higher alps are smaller than in the lowlands.
Teaching the constant angle approach allows a pilot to carry out a forced landing wherever they fly and not just in the locality of their home base.
I failed my first FLWP as I was set up on the largest field on the Isle of Wight and consequently too high...my second was set up after a snow storm...