Remove excess fat from meat. Place meat slow cooker. Cook over low until the meat is quite tender and shreds apart easily (about 8 hours). Remove meat and shred.
Combine 1 to 11/2 lbs of shredded meat with 1 jar of Salsa Verde. This will be spooned between the two layers of Masa Harina.
Preheat oven to 350 degrees. Lightly grease a 9" x 9" square ovenproof baking casserole dish.
Press half of the tamale dough into the casserole dish. Press the mixture evenly on the bottom and up the sides, about 1/4 to 1/3 inch thick. Spoon the pork mixture evenly over the dough, being careful not to spoon in too much gravy. Spread the remaining tamale dough over the filling, trying to make the top portion the same thickness as the bottom.
Fill a large roasting pan with about 2 inches of very hot water and put the uncovered tamale casserole in the water bath. Cover both the casserole & roaster with one layer of heavy duty aluminum foil and place in oven.
Bake for 45 minutes to an hour or until the Masa is set. Let it cool slightly before serving.