Review jobs and the "What to do you want to be? I want to be a / an..." grammar with the class. I did a demonstration using some flashcards with the HRT by asking and answering while pointing to a flashcard on the blackboard. This should take around 3 to 5 minutes.
Give the students a worksheet and tell them to draw a picture first. They can use their dictionaries or Chromebooks for help. Any job is ok (so long as they don't want to be yakuza or the like), and you might get a few surprising answers. One of my students wants to be a nail artist, and one wants to be a gas station attendant. I recommend giving them between 5 to 8 minutes for the drawing and writing section.
After writing the Japanese and English, have the students practice by going around the classroom and asking their classmates. If you have extra time at the end of class, you can have students speak with you, the HRT, or another student to demonstrate the grammar a little further.
Why do you let them draw the pictures first? I would say its better for them to write the sentence first and then draw the picture, because it might take them a while to decide what they want to be and if they spend the whole time drawing, they won't have written anything down.
The drawing comes first because I think it helps puts the students' ideas first and then the appropriate language can follow. It is a somewhat arbitrary decision, but it follows my teaching philosophy of "applying new language to familiar concepts." I will admit that it takes a while, but walking around and reminding them about the time limit helps.