Some everyday words in English have tricky spellings and can’t be read by blending e.g. you can’t blend the words ‘said’ or ‘does’. These are sometimes called high-frequency words, tricky words, or red words.
These words just have to be learned by sight and flashcard-type games are a good way to practise these. These are the red words that children should be able to read by the end of the phonics programme.