Sift the flour, baking powder, baking soda, salt, and sugar together in a large bowl. Blend the bacon grease into the flour with your hands.
Make a well in the center of the flour mixture, then slowly pour in part of the buttermilk and stir. Add just enough, stirring until a dough forms. STOP adding buttermilk as soon as it’s dough – even if you haven’t yet added the full ¾ to 1 cup.
Turn the dough out onto a floured surface. Knead, roll, and pat to shape into a slab of dough about half an inch thick. Use a biscuit cutter to cut out as many rounds as possible (recipe should make 6-8). Of course you’ll want to pull scraps together and roll into a smaller slab to cut a couple more to maximize your yield.
Place biscuits on a baking sheet, so that they are touching. This will provide the support they need to “climb” as they bake. (Optional: Brush tops with melted butter before baking for browner tops.)
Bake for 10 to 12 minutes, until the biscuits have risen and the tops have begun to brown. Serve warm.