Step 1: A mandala is a symbol of the universe, used spiritually and ritually. It's an intricate, abstract, typically circular design.
Step 2: Examine its use in religions. Geometric spiritual diagrams are in Hinduism (e.g., yantras), but the elaborate, meditative creation of mandalas – often using colored sand, then destroying them to represent impermanence – is a key practice in Vajrayana or Tibetan Buddhism.
Step 3: Draw a conclusion. The described process of sacred, meditative creation strongly indicates the sand mandala tradition in Tibetan Buddhism.