To prepare the starter, combine warm water, flour, and yeast in a bowl, whisk until smooth, cover, and refrigerate overnight.
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.
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.
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.
Bake for 10 minutes, swapping racks halfway. Continue baking until golden brown, another 10 to 15 minutes.