Place 6 cups of water in a large saucepan; bring to a boil. Stir in the hibiscus petals, cinnamon, cloves, nutmeg, and allspice. Reduce heat to medium-low, and gently simmer until the water has turned a deep red, 30–45 minutes.

Stir the chopped piloncillo into the hibiscus water until dissolved, then set aside to cool for 15 minutes.

After cooling, strain the warm liquid into a 1-gallon pitcher through a wire mesh strainer. Squeeze as much liquid from the petals as you can, then discard the petals.