This is just a basic introduction and practice. I'll be using at a school that doesn't allow groups or pair work. So it will be completely teacher directed.
You and the teacher introduce the theme. We won't make groups and we'll just get kids to call out the missing words. Then have them repeat the sentences after the ALT. The teacher should check the meanings as you go along.
Finally they can open their notebooks and write the directions to the hospital. Encourage them to draw a map as well. Once done they will go to the ALT and have the model conversation. Depending on the teacher and the class we might expect them to memorize the directions first.
The teacher should give the students the directions for how to go to the ALT. When ready one student goes to the corridor where the ALT is waiting. They have the conversation and then return. Once they've returned to their seat another student can get up and go to the ALT.
The teacher should have worksheets the students can do once they are done or even while they are waiting. The teacher will supervise the class.