If you are packing for a trip, grab a few resealable plastic bags for your underwear. Leslie Willmott of Smart Packing says it's the best space-saver and also helps maintain hygiene.
Packing your undergarments tightly together in a plastic bag reduces the amount of air inside, in turn minimising the space they need. Then you can stuff them into any available space in your suitcase, unlike having to keep them on top.
An added advantage of clear, resealable plastic bags is that if your bags are checked, the security officer can easily spot your undergarments without needing to touch them.
Willmott also recommends keeping a second resealable bag to store your used underwear on your trip. The video also has suggestions on how much underwear to pack, and she reiterates the nesting method to pack socks.
How to Pack Underwear: Smart Packing & Travel Tips [Expert Village]