There are three central vowel sounds to watch out for. ə (sighing sound uh), ʌ(as in pizza hut) s and ɑː (card).
The tongue is more or less in a flat position for pronouncing these central vowel sounds.
You can become mindful of your tongue position by conjuring up an imaginative phrase that contains these central vowel sounds:
ðə ɡʌn əˈlɑːmPhonetic Translation for “the gun alarm”
Now add some uplifting melody so you can associate it with the tongue position for central vowel sounds:
Check out the video blog version:
Use this rhyme generator https://rhymebrain.com/en so you can create your own central vowel rhyme in the comments section.