There's a bunch of different ways to approach it. A narrative framing device with everything told in flashbacks (which is what all of star wars is anyway depending on how literally one takes the opening card to all the movies), a stroll through the world between worlds is another way to go (the imagery of it is all over the show's logo so they're clearing doing something with it), as is force visions, in-narrative flashbacks, and of course the good old fashioned dream sequence.I wonder how much backstory they will provide on Ahsoka for those that never watch cartoons. We got a little of her in The Mandalorian and the Book of Boba Fett, but this will be her own show (or a sequel to Rebels) where they might need to catch people up on things. Unlike Kenobi, they can't just do a montage of the Clone Wars and Rebels...can they? Or would they actually redo some scenes in live action, just to get people up to speed?
One has to wonder though; exactly what are the essentials that a fresh uninitiated audience *needs* to know about Ahsoka? Not every detail needs to be covered after all. I mean at this point in her story do they need to know about 'Fulcrum'?
I guess beyond her being 1) Anakin's padawan in the Clone Wars who 2) left the order before Order 66; the only point they might need to directly explain is where she was during the OT. Which is handy because that's ground that hasn't been covered yet at all, so it won't feel redundant to those who are already up to date.
I feel like a bigger hurdle is going to be catching everyone up on who Ezra is any why they should care (though I suspect that'll be done more through Sabine's eyes than Ahsoka's.)