Remove the seeds from the guajillo chiles and soak them in hot water for 10 minutes
Blend the chiles, orange juice, vinegar, spices, onion, garlic, and salt until smooth.
Slather the marinade all over the sliced pork making sure you cover all the meat, place it in an airtight container and refrigerate for 2-8 hours. Discard the excess marinade.
Cut the bottom of the pineapple and skewer it into an Al Pastor Skewer Stand (you can use three wooden skewers instead).
Skewer the slices pork one slice at a time until all slices are in place. Finish with a thick slice of pineapple. Slow roast in a 280 F oven for 2 ½ to 3 hours. Then, turn on the broiler and let the meat char on the edges for about 5 minutes. Keep an eye on it because it can burn easily!