Take a spelling test and track your progress: The Flossy Rule.
In a short word after a short vowel, the sounds /f/ /l/ /s/ and /k/ are spelt ff, ll, ss and ck at the end of a word.
"I would like to thank you so much for this great website. I have always been ashamed of my spelling but after a few lessons I am already better. It is filling in all the gaps. Thanks."
Student, France