Raise the back of your tongue to touch the soft palate (velum). Stop the air, then release.

Americans pronounce carpool as KAR-pool (/ˈkɑrˌpul/). The L in "carpool" is a dark L — the back of the tongue rises toward the soft palate, adding a small "uh" quality before the L. This is called the Dark L vs Light L, a hallmark of natural-sounding American speech. It comes out as KAR·POOL. Stress falls on the first syllable — keep everything else short and quick. You'll hear it in sentences like "She prefers to carpool with coworkers to save on fuel costs".
Record yourself saying "carpool" and play it back. The mic stays on your device — nothing's uploaded.
2 syllables, 5 sounds. Tap a syllable to jump to its row, then explore each sound's mouth shape and how it's made.
Press your lips together to stop the air, then release. No vocal cord vibration.

Round your lips into a tight circle. Let your tongue rest in the middle of your mouth, slightly raised.
Keep the tongue tip down and pull the back of the tongue up toward the throat. The 'dark' sound comes from the back.

The textbook way isn't wrong — it's just not how anyone actually says it.
The L in "carpool" is a dark L — the back of the tongue rises toward the soft palate, adding a small "uh" quality before the L. Dark L adds a small schwa-like "uh" before the L. The back of the tongue lifts toward the soft palate.
Stress falls on the first syllable, not the others. Stretch KAR — keep everything else short and quick.
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.