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

Americans pronounce classroom as KLAS-room (/ˈklæsˌrum/). Stress falls on the first syllable — keep everything else short and quick. You'll hear it in sentences like "The classroom was quiet during the final exam" or "The classroom was equipped with modern technology for presentations" — more examples below.
Record yourself saying "classroom" and play it back. The mic stays on your device — nothing's uploaded.
2 syllables, 7 sounds. Tap a syllable to jump to its row, then explore each sound's mouth shape and how it's made.
Raise the back of your tongue to touch the soft palate (velum). Stop the air, then release.

Place the tip of your tongue against the alveolar ridge just behind your top front teeth, the same contact point as /t/, /d/, and /n/. The difference is what happens to the air: for /l/, you let it flow continuously around the <em>sides</em> of the tongue (that's why /l/ is called a lateral). Turn your voice on the whole time. Lips stay relaxed, no rounding or flaring. For the Dark L variant at the end of a syllable, also pull the back of the tongue up and back toward the soft palate.

Drop the jaw noticeably. Keep the body of the tongue low and forward, and don't let the back of the tongue raise toward the soft palate. Pull the lip corners back slightly, almost a starting smile.

Place your tongue tip near the roof of your mouth behind your top teeth. Push air through the narrow gap. No voicing.

Curl or bunch your tongue without letting the tip touch the roof of your mouth. Brace the sides of your tongue against your upper back teeth, and round your lips slightly.
Round your lips into a tight circle. Let your tongue rest in the middle of your mouth, slightly raised.
Press your lips together. Air flows through your nose. Vocal cords vibrate.

Click any sentence to see the full breakdown — every link, every reduction, every flap-T.
The textbook way isn't wrong — it's just not how anyone actually says it.
Stress falls on the first syllable, not the others. Stretch KLAS — keep everything else short and quick.