Say the sound r and hold it — that IS the vowel. Your tongue bunches up in the middle of your mouth and the tip curls back, and it touches nothing at all. 'her', 'bird', 'turn' and 'burn' all have it.
Check yourself: Hold the sound and look in the mirror: your tongue is not touching your teeth or the roof. Now say 'uh', then 'er', and feel your tongue pull back and bunch up.
Watch for: A rolled or tapped r stuck on after a vowel — 'bird' as 'bi-rd'. Arabic, Somali and Urdu all tap or roll their r. In English there is nothing to tap: the r IS the vowel, and it is one long smooth sound.
◆ marks a word that does NOT follow today's pattern — Blumenfeld boxes these on the page. Teach it by heart; do not let the class sound it out and lose faith in the rule.
Say the word, have them repeat it, count the sounds on fingers, THEN write. The count is what stops a child writing the first letter and guessing the rest.