Using just the target language

Yes! It can be done. Although it requires a ton of patience! Take it step by step and demonstrate. Below is a video in which you can watch my colleague Carlos explaining to third graders the game I mentioned before: "¿Qué es?". In this game, some students have objects or flashcards, and others don't. Then, they walk around the classroom asking each other "Qué es", and giving it to the student if the answer is correct.