Heat a small skillet over medium-high heat. Meanwhile, in a small, heatproof bowl, stir together coriander seeds, cumin seeds, peppercorns, cloves, cardamom seeds, bay leaves, dried chiles de arbol, and cinnamon pieces. Sprinkle spices into hot skillet and toast, shaking every few seconds, until coriander and cumin are reddish brown, cinnamon and bay leaves appear brittle and crinkly, chiles are blackened in spots, other spices are slightly ashy black, and the whole thing is highly fragrant, 1 to 2 minutes. Transfer immediately to bowl.
When cooled completely, crumble chiles and grind everything in a spice grinder (or a coffee grinder or high-powered blender) to the consistency of finely ground black pepper. Store in a sealed container in a cool, dark place up to 3 months.