You would probably find it interesting to learn how Russian students understand English and Russian phonetics from their perspective.

At first, let me tell you a story how we learned to pronounce English vowel combinations AY, EY, OY, UY at school. You may find it funny Of course, I know it is not a scientific approach, and it is not phonetically accurate. But it worked!

I think you know that many Russian children learn English as a foreign language at school. In the time of my school ages, most of schools usually offered to choose between three foreign languages to learn – English, German, or French. A foreign language was a mandatory school subject, but the quality of how it was taught then was often quite poor. I am not sure about the nowaday education.

OK. Here’s the story:
We learned how to read single vowels in "open" (date-theme-hide-vote-mute) and "closed" (can-bet-bit-hot-cut) syllables. And then we learned how to read some vowel combinations, including AY, EY, OY, UY.
But nearly ALL my classmates (including myself ) could not understand, why on earth we have to learn those 4 combinations separately!!!
We saw a very simple logic in how it worked.

Let’s consider how a single vowel letter is pronounced in a closed syllable (I’m deliberately giving a Russian transliteration to show how Russian perceive the sounds):
Cat – кэт
Set – сэт
Sit – сит
Lot – лот (we learned British English at school, in American English I would rather right "лат" instead)
Cut – кат
Yes, most of Russians do not even now that the vowels in "cat" [kæt] and "set" [sɛt] are different. And many people even think that "bed" and "bad" are homophones!
Now, let’s consider how vowel combinations AY, EY, OY, UY are pronounced:
Bay – бэй
Whey – wэй (I keep the English letter for "w")
Boy – бой
Buy – бай

So, from naïve Russian perspective, those words just obey the same rules as the words with "closed" syllables (if we put "y" as a final consonant, similar to Russian "й"), compare:
Bat бэт – bay бэй
Wet wэт – whey wэй
Top топ – toy той
But бат – buy бай (yes, the vowel in "but" is [ʌ], but Russians hear it as our "а").

That’s why I could not understand in my school ages why we have to treat "ay, ey, oy, uy" as special combinations, if we can easily do with treating them just as independent letters, "y" being a consonant.

At second, a few words on how Russians perceive their own phonetics.
All Russian children, as well as many adults, believe there are 10 vowel sounds in Russian: а, е, ё, и, о, у, ы, э, ю, я. Although we learn at the elementary school that "е, ё, ю, я" represent sound combinations [йэ, йо, йу, йа] rather than independent vowels, many people quickly forget about that. I used to teach elementary English to some Russian adults, and I was often asked "Is there a rule that “ye” combination (e.g. in “yes”, “yet”) makes the Russian “е” vowel"? That’s how our spelling system cheats us