Given how LLMs work, hallucinations still occur. If you don't want them to do so, give them the facts and tell them what (not) to extrapolate.

How to draw an owl:

1. Start by drawing some circles.

2. Erase everything that isn't an owl, until your drawing resembles an owl.

Simpler: if you don't want them to do so, don't engage the LLM.