Combine flour, salt, pepper, and poultry seasoning in a shallow bowl and stir to mix well.
Cut chicken into bite-sized pieces and dredge in flour mixture, shaking off excess flour. Reserve remaining flour for thickening sauce.
Place 2 tablespoons butter in a large saucepan over medium heat; heat until the butter starts to bubble.
Add chicken pieces and cook, stirring frequently, until they are lightly browned on all sides.
Remove chicken from pan and set aside.
Add remaining butter to pan. When butter is melted add two tablespoons of reserved flour mixture. Cook over medium heat, stirring constantly, until flour has turned golden brown.
Whisk chicken stock into flour mixture. Cook, stirring often, until mixture starts to thicken.
Return chicken to pan and add vegetables. Allow to return to a boil, then reduce heat to low and simmer until vegetables are almost done.
While vegetables are cooking preheat oven to 375°F
Dust one side of one of the pie crusts with about a teaspoon of flour. If using an oval casserole dish, use a rolling pin to roll the crust into an oval shape.
Place it floured side down into a 3-quart casserole dish and press it to a uniform thickness. Make sure there are no breaks in the crust and it comes all the way up to the top of the dish. If necessary, cut a little off the other pie crust to fill in the spaces.
Pour the chicken mixture into the casserole.
Top with the other crust and crimp around the edges, cutting off any extra dough.
Cut slits in the top crust with a sharp knife.
Bake for about 30 minutes or until top crust is golden brown and filling is bubbly.