I am no expert but I have shipped and received many boards over the years
The most important part is to put extra protection over the tip and the tail. Think extra cardboard if you have it. Then lots of bubble and shrink wrap over and around the entire board and then fit it all in one long, thin box.
Tip and tail are most important and it's sometimes difficult to find the right sized box. You can find a longer one and cut it down shorter if you need to.