We've always just bought the bottles, wrapped them well in case of leaks, and put them in our suitcase. Once we even bought 24 of those aluminum Bud Lite bottles, put them in a small suitcase and sent them on their way. They arrived to our stateroom without a problem.
The website you are looking for is www (dot) rumrunnerflasks (dot) com. Use code "REPEAT" to save some money. These flasks work well as they lay flat in your suitcase and are harder to detect. I have also heard of people buying alcohol in port, filling the flasks, and putting them in their pockets (like on cargo shorts) and they go thru the metal detector, no problem, and no confiscation of your alcohol.
We've cruises Carnival 6 times, and the only time I've seen them be picky about confiscating the liquor is on short spring break cruises, but even then, we got ours just fine!
There is some debate about them screening luggage; some say they don't scan all suitcases, and others say yes they do, they scan everyone of them. I have no idea about this but I would hope that they do. And I would say the screeners are more worried about weapons than booze?
