Ahead of time, prepare about 4-10 items that need sorting. It could be a sequence of steps to complete a refactoring, or items that belong in different categories. This should be items they already know about, that are related to the learning hour topic. If the items are a sequence of steps to complete a refactoring, ideally later in the session they will need to do this refactoring.
Randomly shuffle the items and give a copy to each pair. Give them 2 minutes to sort the steps into the right order. Afterwards, share your original list with the steps in what you think is the correct order. Ask people if they agree. Take a short discussion if anyone disagrees.
Alternatively, do the sorting as a whole group. Go through each item in turn and ask people to vote for where to put each one. If people vote very differently on a particular item, discuss why.
This shouldn’t be hard and you are not expecting people to have very different answers. If there is a lot of disagreement, then you have either misjudged how much they already know about the topic, you have made poor choices about what items to include, or your item descriptions are not good enough.
Sorting existing things is easier than coming up with new things, yet it still reminds people what they know about a topic.