Flare your lips and push them away from the face. Lift the middle of your tongue toward the roof of the mouth.

Americans pronounce earned as URND (/ɜrnd/). You'll hear it in sentences like "He earned extra credit by completing the optional assignment".
Record yourself saying "earned" and play it back. The mic stays on your device — nothing's uploaded.
1 syllable, 3 sounds. Explore each sound's mouth shape and how it's made.
Flare your lips and push them away from the face. Lift the middle of your tongue toward the roof of the mouth.

Touch the tip or front edge of your tongue to the roof of your mouth behind your teeth. Air flows through your nose.

Touch the tip of your tongue to the roof of your mouth just behind your teeth. Add vocal cord vibration as you release.

The textbook way isn't wrong — it's just not how anyone actually says it.
Americans use a relaxed retroflex R — the tongue curls back rather than rolling. The R is one continuous sound with the vowel before it, not two separate sounds.