mix all dry spices except 3 tsp of cumin
cut roast in have and rub spice mixture liberally over both halves. place in slow cooker with green chilis and cook on low for 8 hours. (can also use instapot for 45 minutes)
once pork is tender, remove from slow cooker and shred. add pork and 3tsp cumin back to slow cooker and stir.
serve on warm tortillas topped with letuce and jack cheese