Mix the flour, salt, pepper, and poultry seasoning in a medium-large mixing bowl.  Add the turkey and toss until the pieces are thoroughly covered. Make sure to shake off excess flour when you put it into the pan and keep the leftover flour mixture for later.

Heat 1 tablespoon of the vegetable oil in a large, deep skillet over medium-high heat.  Brown the turkey pieces in batches, about two minutes per side.  You don’t want them to be too crowded while cooking.  Add more oil in between batches if necessary. Transfer all turkey pieces to the slow cooker once all are cooked.

Add more oil to the skillet over medium heat.  Add the onions, carrots, celery, mushrooms and potatoes and saute until the vegetables start to lose their raw look, making sure to stir often.  It will take about 4-5 minutes.

Add the leftover flour mixture and stir until the vegetables are well-coated. Add the chicken broth and heat until boiling.  Stir constantly until the sauce is slightly thickened.  Transfer to the slow cooker and add the dried cranberries.  Stir to combine, cover the cooker and cook on low for 6-8 hours.

Preheat the oven to 375 degrees.  Remove the pie crust from the refrigerator and let it get to room temperature.  Roll it out on a lightly floured surface to fit the top of the slow cooker.  If your slow cooker insert cannot go into the oven (which mine cannot), transfer the ingredients to a dutch oven or deep cast iron pan that can go into the oven.  Place the rolled out pie crust over the turkey stew and roll the edges up the sides so that the stew is fully covered.  Put a few slits into the top of the crust and place in the oven.  Bake until the crust is browned, about 25 minutes.