Combine flour, yeast, sugar, oil and hot water in a medium bowl and stir until dough forms. Turn the dough out onto a clean surface and knead until smooth and elastic, about 8-10 minutes. Let rise in a lightly oiled bowl, turning the dough in the bowl so the surface is coated. Cover with a clean towel and let rise in a warm place until about doubled in size, about 45-60 minutes.Once dough has doubled, punch down dough and roll into a log. Cut into 10-12 equal pieces and roll each piece into a ball. Let rest on a parchment-lined baking sheet for 10 minutes. Roll out each ball into a 4-5" circle. Brush the top of the dough with sesame oil, fold in half (don't press down) and place on a square piece of parchment. Cover with a clean tea towel and let rise another 15 minutes. Place the dough in a steamer (with the parchment so it doesn't stick), making sure that the buns don't touch. Cook in batches as necessary. Steam on high for about 8 minutes.Leftovers can be refrigerated for a couple days, or frozen for a month. Just re-heat under a damp paper towel in the microwave for 30 seconds or so. Keep an eye on it.Stuff the bao your favorite things, or try this bulgogi recipe!