Consonant /I/ and /r/ - SS1 English Lesson Note
To produce /r/, let the tip of the tongue nearly touch your alveolar ridge. But when you make the /l/ sound, you let the tip of your tongue make contact with the alveolar ridge and also force the air out through the sides of your tongue.
Example
/l/​​​​​​​                /r/
London​​​​​​           RiotÂ
Lamb​​​​​​​             RunÂ
Follow​​​​​​​           RoyalÂ
Challenge​​​​​​       SproutÂ