(Optional - skip if omitting garlic) Thread the cloves of garlic onto a metal skewer, then carefully roast/blacken them over an open flame (I use a gas stove, but you could use a barbecue too). If you don't have a flame source, you can blacken the cloves in a very hot cast iron pan instead. The idea is to thoroughly char the cloves, but not to roast them all the way through. Set the charred garlic aside to cool.

Remove the stems, seeds, and membranes from the dried chilies. You may find it easier to do this after toasting; I personally shake out the seeds before and after to remove as many as possible.

Toast the chilies by either adding them to a hot frying pan for about 2 minutes (turning occasionally), or by microwaving them for 20-30 seconds. The toasted chilies should be pliable and very fragrant.

Place the toasted chilies in a small bowl along with the Seville orange juice (or citrus substitute), vinegar, and salt. Soak for about 10 minutes.

Peel the garlic (if using) and combine with the chilies, juice, vinegar, and salt in a blender, spice grinder, or mortar and pestle. Blend/pulverize until the salsa is uniform. Add a little water for a thinner consistency, if desired. Let the salsa sit for 20-30 minutes if possible in order to balance the flavours.