An eight-week habituation plan built for cats rather than dogs — handling, the carrier, sounds and household life. Gradual, on your kitten's terms, and honest about what the socialisation window actually is.
For a cat that's usually counterproductive. What matters is habituation — handling, sounds, the carrier, household life — not a stream of visitors wanting to hold a kitten who never asked to be held.
By which point the carrier only ever appears before something unpleasant. It's arguably the highest-value thing you can teach a cat and it takes five minutes a week, starting on day one.
Hands used as toys with an eight-week-old is charming. The same behaviour in a four-kilo adult is the most common complaint owners have, and it's very hard to undo once established.
The primary sensitive period in kittens runs roughly from two to seven weeks — largely at the breeder's or rescue's, before you had any say. That's not a reason to panic; it's a reason to focus on the habituation that keeps working.