Place chicken, onion, celery and salt in a large pot. Add enough water to completely cover the chicken. Bring to a boil; reduce heat and simmer until chicken is tender and cooked through, about 1 hour.
Remove chicken from broth and cool enough to handle. Pick chicken off the bones and discard bones.
Grease a 9 x 13-inch baking dish.
Remove celery and onion from broth. Measure broth and return 3 cups to the pot.
In a small bowl, blend 1/4 cup flour with 1/4 cup water to make a smooth paste. Stir into hot broth. Cook 5 to 10 minutes or until broth is thickened. Season with salt and pepper. Pour over chicken.
In a large bowl, combine 2 cups flour and 1 teaspoon salt.
Cut in shortening with a pastry blender or two knives until mixture forms coarse crumbs.
Sprinkle with cold water and mix until dough hold together and will form a ball.
Roll out on a floured board or pastry cloth to about 1/4 inch thickness.
Cut into strips and place over the chicken. Bake at 375 degrees F until the pastry is golden brown.