For Alexa to spell a word, say spell followed by a word that you would like her to spell.
For checking your spellings, say check my spellings. Alexa would then read out words from a list. For every word, Alexa would ask you to spell it. To spell, you say spelling is followed by your spelling of the word. Alexa would check your spelling and tell you whether it is correct or not. At the end, Alexa would tell you the number of words you spelt correctly.
For checking your For checking your pronunciation, say check my pronunciation. Alexa would then pick a word randomly, spell it out to you and ask you to pronounce it. To pronounce say word followed by your pronunciation. Alexa will check your pronunciation and tell you whether it is correct or not.
Acknowledgement: The skill is using wordnik APIs to get random word for checking spellings and pronunciations.