To make the /ɔɪ/ sound: /ɔɪ/ is a diphthong, which is like a combination of two different vowel sounds. To begin, place your tongue at mid-low height in your mouth, shifted toward the back, to say /o/. Round your lips into an “o” shape as you do so. Then, as you vibrate your vocal cords, lift your tongue high in the mouth and shift it toward the front, to say /ɪ/. The transition between these two positions should be very quick.