Answer:
Inside a burning house, this thing is best to make. And best to make it quickly, before the fire's too much to take.
There is one in every corner and two in every room.
I'm a green veggie that looks like a tiny tree.
What can be any size or shape and gets bigger the more you take from it?
Every country has one, though we are not the same. Waving to our citizens, throughout the wind and rain. What is it?
I am your mother's brother's only brother in law. Who am I?