Conversation so far:
What is Francis Bok's escape story?
Francis Bok waited three years, until 1996, before he tried to escape again.
When did Francis Bok escape slavery under Giemma?
Bok finally escaped from Giemma when he was 17 years old by walking through the forest to the nearby market town of Mutari.

Question: How did he escape?
Self-contained rewrite: How did Francis Bok escape slavery under Giemma?