Learn three short sounds: short I (ih), N (nnn), and short E (eh), and notice how quick each one is.
I says ih, like an itchy nose. N says nnn, humming right through your nose. E says eh, like eggs.
Ih, nnn, eh -- say each one and notice where you feel it.
Mastery looks like: They can produce the short I, N, and short E sounds and sort familiar words correctly among the three.
Common stumbles: Saying letter names instead of sounds; blending the three short, similar sounds together.