Long or short, I build them the same way. My way:
3/8" plywood, 1"X4"s, 2"X4"s, 1-1/4" staples, coated deck screws and a lot of bubble wrap. (Next time, I won't fully block the corners and gain some length, or just plan on building it longer.)
Top (only) is just screwed down and locations identified with magic marker. TOP is identified and indexed in. & exterior.
Shipping instructions are placed inside, on the wood shell as well as the cardboard sleeve with magic marker and then overlayed with 8-1/2"X11" shipping instructions and completely taped/sealed down.
New cardboard boxes from Walmart (turned inside out, so clean, unmarked surface-cheap and no fuss) center wrapped and ends sleeved over (makes opening tres-easy)
Why you ask??
The USPS and/or UPS people:
Rule 1: It's not a gun or firearm, antique reproduction suits me; an extremely expensive antique reproduction.
Rule 2: Stronger is better
Rule 3: Send Priority/Expedited with Tracking, etc. Spare no expense.
Rule 4: Insure the living $#*! out of it. Fear is a good thing. They ship super FAST and handle w/EXTREME CARE.