the holes in the bottom (sides) are for the air intake, most use three or four holes.
I am not sure how hot the bottom gets but I have been thinking about building a sand box to put it in so that I can move mine to the deck also.
As far as a firebox, mine is made from a coal grate from a 221/2 weber, wrapped in 1/2 expanded metal. The grate is 2 1/2 inches from the bottom with aprrox 10 inches left to hold the charcoal.
A friend of mine uses a large clay dish (think planter) in the bottom of his for easy clean up.