For anyone who has had a lot of trouble with learning the Korean alphabet on Duolingo
Turns out what Duolingo's teaching you is syllables, not the alphabet itself. I looked it up, and found this site: http://learn-hangul.com/#learn-hangul
It teaches you about the actual 'letters', which are then grouped into syllables. It made learning the syllables with Duolingo leaps and bounds easier!
UPDATE: It helped me so much that I had it memorized two days later!
Bless. I had such trouble, after I had heard the Korean alphabet was really easy to master. Thank you for the resource!
You can also click on the little light bulb icon next to the start button for any particular skill set to get a brief lesson. Alphabet 1 has some info on syllable blocks, vowels, iotised vowels and diphthongs; Alphabet 2 on consonants; Alphabet 3 on the romanisation standard Duolingo uses and common transliteration to Korean; Basics 1 on nouns, articles, 'and' conjunctive, copula, plurals, omissions in Korean; and etc.
I'd highly recommend complimenting Duolingo with other sources. Language books, other websites, tutors if you can, eventually other media like movies, music, newspapers.