The easiest way @anne-kamilla would be to just resend it as a another campaign. Clone the email so you don’t have to recreate it, create a segment of anyone who opened or clicked the first email, and then exclude them from the resend.
You could do it as a flow, but you’d have to create a segment of everyone that you want to receive it, set up the flow, back populate the flow, etc. It would be more time consuming to do it that way.
The only time I would say it’s worth it to do the flow way is if you have a lot of contacts who are unsubscribed but still need to receive the message. In that case, I would do it in a flow so you can have Klaviyo support mark the email as transactional.