Three options, depending on how many ties and what else I am packing and how space constrained I am.
1. Roll the tie and put it in a shoe. The rolled tie, on its side, will fit perfectly in the heel of the shoe and is completely protected. I usually stuff a pair or two of socks in first, so making full use of the shoe as storage. Put each show in a separate bag - big ziplock or I collect fabric shoe bags from LH C flights. The imposition of a numerical relationship between ties and shoes may not suit everyone.
2. Use an Eagle Creek Pack-it folder. Fold and arrange all shirts in Pack-it. Then lay a tie diagonally across the shirts and wrap around. As many ties as necessary can be crossed over each other. This works great if you are not packing shoes and option 1 is not possible.
3. A folding tie holder, as mentioned before, when I have a voluminous bag that I will check in. But I find they are a little short and unless you take care, you can get a horizontal crease that will be just below the knot. I solve this by folding the tie in half, then folding again to put in the holder, so that the main part of the tie now has a layer beneath it when folded, so less likely to crease.
An as yet unused ultimate option is to switch to bow ties, which pack much more easily, but tend to label one as a bit eccentric, especially in the USA.