Personally, when I do one shots, I make or use pregens, and have the players use those. That way you can all get right into the story and go. Most players, when doing character creation want to spend time and get invested in that. Then you have a player with emotional investment in a character beyond the one shot. If you are choosing to use it as a launching pad for a campaign, you might have character creation, but even then I personally would rather use pregens to show them the world. Then before the actual campaign started, you could have a character creation session where they made their own for that universe.
Doing it that way also eliminates much of the 'notice time' that you mentioned, as they can hop in and play on a whim. I usually run superhero games, as as such it is easy for people to hop in and get an idea of what is going on and who their characters are. When doing a D&D game, I would just make a character or two for each class you want in the party (maybe a male and female of each) and then let the players pick a class.