To prepare the starter, combine warm water, flour, and yeast in a bowl, whisk until smooth, cover, and refrigerate overnight.
The next day, dissolve yeast and sugar in warm water and let it rest for 15 minutes until bubbly.
Mix in lard and salt, followed by 1 cup of flour, forming a sticky dough.
Add the starter, then gradually incorporate the remaining flour, reserving 1/2 cup.
Knead on a lightly floured surface, adding flour as needed, until a soft, tacky dough forms.
Transfer to a greased bowl, cover with a damp towel, and let rise until doubled, about 2 hours.
Line two baking sheets with parchment and cornmeal.
Shape the dough into two 12-inch loaves, rolling tightly and slightly flattening the tops.
Transfer to baking sheets, dust with flour, cover lightly, and let rise again for 1 1/2 to 2 hours.
Preheat the oven to 400°F (200°C).
Score each loaf with a shallow slit, mist with water, and bake for 10 minutes, swapping racks halfway.
Continue baking until golden brown, another 10 to 15 minutes.
Cool on a rack before slicing.