The above matrix and word sums demonstrate (once again) the morphological nature of English vocabulary. Once you have established the correct spelling of the base <friend> : fri + end or f.r. (i)e.n.d as shown here you can used the above matrix and word sums to build on the words in this morphological family. This should provide opportunities for rich discussions of the various usages and meanings of the words involved. Discussions about nouns, verbs, and adjectives can all come in handy. Which words in this family are nouns? How do you know? Which are verbs? Which ones do you normally use? Which ones are adjectives? How can you tell? Which words are opposites or synonyms? Can you switch (or substitute) different forms of the words in the same sentences and see how the meanings change? Can you use all of the words in sentences?
As you resolve the word sums, you will have to draw attention to the <y> / <i> relations: replacing <y> with <i> in a spelling when a morpheme is added to a stem which has a final <y>. Thus, you do not keep the <y> in a spelling when it no longer final. So <friendly> has a final <y> but when we write <friendly + er> we replace the <y> with <i> therefore producing <friendlier>. English words do not end with final <i> so we write <y> instead and when the <y> is no longer final, we revert to <i>.