I think a bunch of cottagecore creators have talked about how the fantasy is the cottagecore life but without the labour.
That seems to contradict your original statement that cottagecore implies slavery, because if it did then this would be redundant and there would be no need for the "but".
Cottagecore implies labor, yes. If someone is saying they want a cottagecore life without the labor, then they've probably got their head too far up in Wuthering Heights and imagine themselves as English Gentry. That doesn't define cottagecore, though.
Most people who like cottagecore enjoy doing things themselves. Fibercraft of all kinds, soapmaking and candlemaking, baking from scratch. None of that implies slavery, and if you think it does then I would ask where you think those things come from when you buy them from the store.
It's not merely an aesthetic. Just like solarpunk, the aesthetic has been separated from the lifestyle and sanitized, but not in all cases. Homesteading, making things from scratch, is very much a lifestyle.
"Cottage industry" is already a term for people who sell things they make small-scale in their own homes. That seems economically empowering, no? Seems like it would be an integral part to any real solarpunk community, so it makes sense that there's a connection between solarpunk and cottagecore.