For the fluffiest ube bread, allow your dough to rise in a warm, dry place. I use my oven for this. I preheat it to 100F then turn it off just when I’m about to knead my dough. This way, the temperature would have gone down to 90F when I put my dough in. You can also use the keep warm feature of your oven if you have it. For the second rise, I usually just leave the dough out on the counter covered by a damp tea towel.