Castle is pronounced KAS-əl (IPA /ˈkæsəl/). Skip the 't' — say 'KAS' then 'ul' smoothly together.
IPA: /ˈkæsəl/
Syllables: KAS · əl
Common ESL mistake: Learners pronounce the 't' saying 'cas-tul' with a /t/.
Tip: Skip the 't' — say 'KAS' then 'ul' smoothly together.