The spelling choices for the sound /k/ at the end of a word can be grouped into 3 main choices:

This movie gives a multi-sensory activity to use with your learner to help them work out and remember the spelling choice

Here is the task sheet as described in the movie: http://www.gdss.glasgow.sch.uk/Websites/SchSenRosepark/UserFiles/file/Spelling/written%20task%20for%20sound%20k%20at%20start%20of%20word.docx

This link gives you a list of words with /k/ endings for word sorting activities: http://www.gdss.glasgow.sch.uk/Websites/SchSenRosepark/UserFiles/file/Spelling/words%20to%20help%20explain%20spelling%20k%20at%20end%20of%20word.docx   

There are rare times when we use 'ch' as the spelling for example loch, stomach, anarchic.

Where there is a long vowel sound then generally the letter k is used, sometimes with a silent e, for example:

steak, break, beak, peek, oak,   lake, bake, rake, make 

Remember - as long as the meaning of the word is clear it will be understood and accepted - don't get over anxious about spelling choices!