Line a 8x8 baking pan with parchment paper and preheat the oven to 450F/235C.
Combine the flour, salt, baking powder, and sugar together in a large bowl.
Mix in the frozen shreds of grated butter.
Make a well in the center of the bowl and pour in the milk.
Use a spoon to gently combine the dough until it starts to clump together.
Transfer the biscuit dough to the baking pan and press it to fill the entire pan. Use your fingers to smooth the top of the dough and fill in any cracks in the dough. This keeps it from falling apart after baking.
Bake for 15-20 minutes, or until the top is a light golden brown.
Let the pan cool on a wire rack.