Curl your tongue tip up and back, and do NOT let it touch anything. Round your lips a little. Voice on — rrrr.
Check yourself: Mirror: lips a bit round, tongue not touching. If it touches, you get /l/ or a tapped r.
Watch for: /l/, and the rolled or tapped r of Arabic, Somali and Urdu — all three roll it. English does not.
◆ 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.