Enter the class and project (or write) some questions for your students to write them on their notebook. Tell them that they are questions about a text they are going to read or listen.
After they have copied (or written after you have dictated them) the questions tell them that you cannot find the text or that you have forgotten it.
Say to your students (in a theatrical way) that they will have to invent the answers, no matter what they write.
After having written the answers make them read the answers and choose one for each question. The students have to copy the answers , which will be the basis for a text they will have to write. The text will have to contain the answers that were given to the questions.
I hope it is clear enough. If it isn't, please tweet me @eugeniomondejar