A mini lesson is a short lesson segment that is based on a specific lesson or topic. It is not like a teaching technique which is a general teaching method that can be used in many situations. They are not object lessons which rely on an object to teach a gospel principle and are usually lesson openers or closers.
Mini lessons are content specific and meant to be a part of the doctrinal teaching, or meat, of your lesson. A mini lesson usually takes between 5-30 minutes to present. I recommend that you plan your lesson time to include several mini lessons. The change in subject and activity will help keep students engaged.