She told the audience that the project is a unique experiment in the UK, if not the world, and emphasised that the internet is a crucial platform for the future of comment and debate.
However, part of her role has involved convincing the newspaper's columnists - who are accustomed to the prestige of newspaper publishing - that the internet is vital to their future.
"This is where commentary is refining itself," she said.
"You have to think 'where is this competitive landscape going?' - and it is already there. Unless you take your writers there you are already dead."
There is no reason why a traditional journalist would take notice of the web, she said, but that she would be doing a disservice to the newspaper's columnists if she did not show them why their major competition is now online.
"One of the strongest resources of a journalistic brand is its commentators," she said.
"The idea of giving commentators individuals blogs was slightly worrying for all sorts of reasons, but this will be a collective voice for the kind of people we want to talk to."
US celebrity blog the Huffington Post has been cited as an influence for the project because it quickly became a powerful platform for respected columnists.
She said that columnists can now be challenged by anyone with an idea and a simple blogging platform - writers no longer need an international news organisation behind them.
"There is an old-fashioned debate that still goes on in the mainstream British media about the differentiation between bloggers and journalists," said Ms Bell.
"But blogging is just a fantastic piece of software. It doesn't mean that bloggers can't do journalism or journalists can't do blogging. It's just a different way of reaching the audience that now wants links and expects to be able to answer back."
Comment is free will feature posts from selected commentators and columnists on the front page, and writers can also promote their own books, blogs and projects on individual home pages. Ms Bell added that columnists will be paid a small fee for their work which had been pitched to them as an equivalent to the appearance fee they might receive on Radio 4's Today programme.
The Guardian is experimenting with asking readers to register before posting while they assess the audience that the project attracts.
Free daily newsletter
- 5 key considerations for ethical virtual reality storytelling
- The Guardian relaunches its documentaries section to feature longer films
- Tip: Remember this advice for keeping your blog focused and on track
- The Guardian is 'putting the interactive back into interactive journalism' with RioRun
- Trust and credibility: What digital trends and values will shape tomorrow's news?