Preheat oven to 200F degrees.
Place roast in large roasting pan or dutch oven.
Do not add salt or water.
Cover with tight lid and roast about 12 hours until well done (or cook roast with 1 cup water in instapot 35-40 min.
Drain meat, reserving juices.
Cool meat, then remove bones.
Shred meat and set aside.
Melt shortening in a large skillet.
Add onions and green chillies. Saute one minute.
Add green chili salsa, garlic powder, flour, salt, and cumin.
Cook 1 min over medium low heat.
Stir in reserved meat juices and shredded meat.
Cook five minutes until thick.
Cool.
Put about 3 cups mix into three one quart freezer containers, leaving 1/2 inch space at top.
Seal and label containers.
Freeze
Use within six months.