When teaching children, who are beginner readers, how to join to the leen letters wow and yaa, what is the best way to explain to them the length without comparing it to that of a vowel?

Question
Assalamu'alaykum wa rahmatullhi wa barakatuhu

I noticed from one of your previous answers that vowel timings cannot be compared to saakin letter timings because the system is not the same.

When teaching children, who are beginner readers, how to join to the leen letters wow and yaa, what is the best way to explain to them the length, without comparing it to that of a vowel? Also, what is the correct sound when joining to the leen letter yaa. Is it correct to compare it with the sound of English words like 'play and tray'?

May Allah reward you for your efforts.

Answer
Wa alaikum assalaam wa rahmatullahi wa barakaatuh
Children pick up a great deal by listening to a qualified teacher read and them reading after the teacher.  In general it is not recommended to compare to English sounds as they aren't the same for the most part, and play and tray are good examples of this.
In English "tray" and "play" end with an "A" sound, not a ya' sound, and has imaalah in it, which is not the correct sound of the leen.

If the teacher pronounces correctly and repeats it, insha' Allah the children will pick up the correct sound.  If there still is a problem in the timing, the teacher can say "that is too long" or "that is too short".  If the leen sound itself is not correct, it should be broken down to a fathah on a letter, repeated for emphasis, then a ya' saakinah (or wow) added after the vowel sound is firm in their minds, with emphasis on the correct articulation for the ya' and wow. 

Wa iyyaakum.  May Allah make you of the best teachers of the Qur'an.  Ameen.