Exciting news! My most recent article on Medium covers the topic here titled “This or These?”
The Medium article has much more information, examples and practice ideas.
I have a free-access link to the article on Medium — if you are not a Medium member, there is a monthly reading limit, but with my link you can read the article even if you have already reached the limit! Here is the link: Pronouncing English Vowels. Some of the most difficult pairs: Long-E vs. Short-i
I hope it helps you learn even more! ENJOY!!