Remove the pork shoulder from the refrigerator while you prepare.
To a large bowl add the peppers and cover with boiling water, soak until softened, about 30 minutes.
To a small bowl add the oregano, cumin, chili powder, cinnamon and salt, mix well.
Rub the spice mix all over the pork shoulder.
Drain the peppers and add to a blender along with the pineapple juice, garlic, cumin, oregano and salt. Blend until smooth.
Add the pork shoulder to a slow cooker and pour half of the sauce over the pork. Cover and cook for 4 hours on high or 8 hours on low.
There will be liquid in the bottom, do not discard. Remove the bowl from the slow cooker and use 2 forks to shred the pork in the bowl.
Mix in the rest of the pepper pineapple sauce.
Serve in a flour tortilla with fresh pineapple salsa.