Building a fire? Vivian knew how to do that! In fact, her parents thought her how, before. Since she was underage, she obviously wasn't allowed to conjure fire during camping and hiking. So yeah, she knew quite some information about creating a useful bonfire. However, she still went to gather around and observe how to build one from the Groundskeeper, Mr. Baldvinsson. Once the demonstration was finished, Vivian went to pick up her materials and chose a fire-pit a little bit near where Professor Vance was.

After settling down on her place, Vivian took the smaller splinters and placed them at the middle of her pit. With the bigger pieces of wood, Vivian held them together from the tip and positioned them to resemble a tent. See? That was simple. With that finished, the Slytherin stood up and moved backwards a little before sending an "Incendio!" with the wand movement thingy at her cluster of wood.

And there it was, her bonfire was set ablaze. She quietly thought that, if Andrei were around, maybe she'd let him do that fire-taming thing he liked to do. Would have been really interesting to see.