In casual American English, "How do you spell your last name?" sounds like "HOW doo yoo SPEHL yor last NAYM". Three things happen here, and the headline one is the Silent T/D Across Words: a consonant in the cluster between words drops out. Keep stressed words long, unstressed words short, and link the consonants forward into the vowels.
Now you try.
Read the sentence out loud at native speed. The mic stays on your device — nothing's uploaded.
What makes this sentence sound American.
The "" at the end of "last" is dropped before the consonant starting "name" — the surrounding consonants flow directly together — common in flowing natural speech; in careful or formal speech, the sound is often kept. This is called the Silent T/D Across Words, what turns word-by-word reading into actual conversation. It comes out as last.
What's happening in this sentence.
Small tricks that turn a textbook sentence into how an American actually says it.
Common pronunciation mistakes in American English.
The textbook way isn't wrong — it's just not how anyone actually says it.
Treating every L the same.
The L in "spell" 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.
Pronouncing every consonant in the cluster.
The "" at the end of "" is dropped before the consonant starting "" — the surrounding consonants flow directly together — common in flowing natural speech; in careful or formal speech, the sound is often kept. The /t/ or /d/ at the end is dropped — surrounding consonants flow directly.
Pronouncing the function word too fully.
"do" is a function word — in connected speech, the full vowel reduces to a quick "" sound and consonants may simplify. Full vowel reduces to schwa /ə/ or other weak vowel. Consonants may simplify.