Someone asked me recently how to put a speech together. Well, dependent on the subject in hand, it does not differ very much from this example in the link.
Read it and see what I mean. It is structured well and would need planning well for a minute or three before you start writing. Because you are only limited to 25 and 35 minutes in Section B of the exam, it will not be this long.
Have a go at one on a subject of your choice, whatever floats your boat!