I recently shipped a frame and a complete bike in the same box. It was kind of a pain. There was a lot of packing and a giant box involved. Thankfully, my LBS provided me with a fat bike box. It was giant (not really, I think it was Specialized, if we’re splitting hairs), it was sturdy, and it got both bike and partial bike to the recipient in a condition that he didn’t complain about.
Bonus—he now has a box that he could use to ship an alligator to someone. If there were alligators free roaming in the Midwest that he wanted to ship somewhere.
The pink frame is a 54-56cm with a stuck seatpost.