In case someone else comes back to this thread, the Swiss post sells cartons that are adapted to 0.7-1.0L wine bottles. A much better option that doing something home-made. I would still add some bubble wrap to fill out the carton.
The carton is the
PostPac Eco 5. They are available in the Post office.
Link to show you what it looks like (don't panic, the cost shown is for 10 boxes):
https://shop.post.ch/shop/en/stamps-...eco-5/p/730841
At the bottom of the page, they have a link for the Customs part of the project.