Many Latin American recipes call for ground dried peppers of various textures; some are processed to a very fine powder, while others are as coarse as the hot pepper flakes that are sprinkled on pizza. Prepared ground peppers are available in markets, but nothing beats the pure flavor and freshness of home-dried peppers ground to your taste. If using already dried peppers, clean and prepare them as described on this page. You can toast the peppers briefly if you want a bit of a smoky flavor (see this page), but I prefer to skip that process to enjoy the essential flavor and color of the dried peppers.
To make pepper powders, butterfly the dried peppers if they are large enough. They should be dry to the point of brittleness. If they are still pliable and soft to the touch, spread them on a baking sheet and place in a 200°F/95°C oven until completely dried, usually about 1 hour. Rotate the baking sheet and flip over the peppers every 30 minutes to dry evenly. Let cool completely. Break into bits by crumbling between your fingers or chopping with a heavy, sharp knife. The smaller the pepper bits, the easier they will be to grind. Grind to a powder in a spice mill or coffee grinder. I like a coarse texture, but grind twice if you prefer a very fine powder. If you have a large, powerful food processor, you can grind large amounts in one batch to the desired texture. Or use the food processor to get a coarse powder and then pulverize that into a finer powder in a coffee or spice mill.
