I always spray foam insulation inside the carton. This keeps the carton contents from shifting.
Bicycle Packing
I take the fork and front wheel off and leave the rear wheel on the frame.
I then wrap 2" foam pipe insulation on the wheels around the tires and rims and also use 3/4" pipe insulation on the frame tubes. 1/2" pipe insulation on the seat and chain stays. Use 3/4" pipe insulation on the fork tubes. Use plastic zip-ties or packing tape for fastening pipe insulation. Use bolt, washers and nut to reinforce the fork at the hub axle dropouts.
Then bubble wrap every thing. Dont use more than one layer. Pack the seat in bubble wrap separately. Take the pedals off.
Remove the handle bars from the gooseneck and cover the bars with 3/4" pipe insulation.
Use a standard Specialized bicycle carton for the frame with rear wheel and a Specialized bicycle wheel carton for the front wheel and misc. Specialized bicycle cartons are the strongest.
Wrap all parts with large heavy duty trash bags and tape openings. Then have handy 8 cans of expanding foam purchased from Home Depot. Lay a bed of foam on the inside bottom of carton where the upside down frame will be positioned. Don't go crazy with the foam placement. Remember it expands. Position the upside down frame in the bed of fresh foam then continue to add foam to the spaces between the carton and the frame. Use long disposable gloves. Foam has to wear off your skin or use nasty acetone to remove. You can spritz water on the foam to accelerate the curing. Now add foam popcorn to the spaces and add any small parts. Copy this procedure to the front wheel and fork carton (smaller wheel carton). The expanding foam fill will guarantee that the bicycle and parts do not become piercing projectiles that would rupture the cartons and cause catastrophic damage to the bicycle itself and also create a pathway for losing parts.
Buy a jumbo Sharpie marker and write fragile, keep upright and do not stack on top of box.
This works every time for me. I learned this lesson the hard way. 99% of all damage of contents are from not securing the contents from moving inside the carton.
