Most people know how fire works. Heat meets fuel and oxygen and results in the chemical reaction of rapid oxidation called fire. Even adults who can explain this reaction in much more detail than I can show a depressing lack of ability to apply that. But you are all do-it-yourselfers, so you'll get it right. If you are absolutely confident (or plan on using a whole lot of expensive petro-chemicals) by all means move-on.
Fire needs fuel, oxygen and heat. If you hold a candle to a log, it will not light, but why? There is certainly enough fuel (see big log), and there is air all around it, and I have heat. Formula no work...Og no cook dinner. There are some people who understand this, yet still pile logs on top of each-other and stuff the whole thing to the gills with newspaper, and wonder why the newspaper just smolders and goes out.
Two keys here: surface area, and airflow. To catch a flame (and especially a spark) you need as much surface area as possible for your flame to catch (which is why newspaper works so well.) But you also need air to be able to circulate and get to where the flame is. If you need a reason, look up oxidation. In a fire, cool air has to come in from the bottom to replace the hot air escaping from the top. Keep that in mind when building any fire.