/?/ is a back vowel sound made with the lips slightly rounded.
The tip of the tongue is relaxed and touching behind the lower front teeth for all vowel sounds.
To make the /?/ sound, the back of the tongue needs to be a bit higher than the front of the tongue...
...and the lip corners are slightly forward like this: /?/, /?/.
A common challenge with the /?/ sound is that the speaker will overround the lips and bring the tongue up too high.
This creates the /u/ sound.
So a word like "could" ends up sounding like "cooed."
A great way to practice the /?/ sound is in relation to the /u/ sound.
So use your hands to mirror what the tongue is doing and try this along with me.
/u/, /?/, /u/, /?/.
Can you feel how the tongue drops and the lips are more released for the /?/ sound?
Let's try this again.
/u/, /?/, /u/, /?/, /u/, /?/.
Now let's try some words that contrast the two sounds.
Look, Luke.
Full, fool.
Pull, pool.
Would, wooed.
And now a few sentences.
Finally, the fool was full.
The horse should be shoed.
Keep up your practice on EnglishCentral and good luck!