It's a good one to teach straight after the ai/ay pattern as, although it's not as commonly used, it follows a similar pattern.
The "key" words I find useful for learning this letter pattern are boy and toy for /oy/ and boil or join for /oi/.
It's also fun for children to say "Oi!" You can easily make up an "Oi!" game: make some word cards with "Oi!", boy, toy, Roy, Troy, Joy, annoy.... Children can take turns to make up an "Oi!" sentence, e.g. "Oi! Roy! Don't break my toy!" - they need to hold up each card as they say the word. If you like, they can write down their "Oi!" sentence or story.
You can download the "Oi!" game instructions here:
Here is a worksheet that you can download for children to use to list oi/oy words: