In a large bowl mix together flour, salt, baking poder and baking soda. Cut in the shortening until the mixture forms coarse crumbs.
Make a well and add 1 cup buttermilk. Quickly cut dry ingredients into the buttermilk to form a sticky dough. Add more buttermilk as necesary.
Turn out the dough on a floured surfaceand foldover itself 3-4 times. Press out to 1/2 to 1 1/2 inches thick: biscuits will double when cooked. The larger size allows for modest eating of only halves. Section with a 3-inch cutter or floured rim of a pint glass abd arrange on an ungreased cooke sheed. Optionally brush with buttermilk for rounded top.
Bake at 375F for 20-25 minutes or until golden.