Boot to Skin
Bootpack sections, especially in the sprint event, often end with more skinning. Transitioning from booting to skinning is the shortest transition and often only takes a few seconds.
Doing a boot-to-skin transition in less than 10 seconds is possible with enough practice with the right gear. Think of 20 seconds as a maximum.
The following method is one of many. Different body mechanics and levels of flexibility may require some adjustments. Practice it a lot, and then make it your own.
Entering a transition zone is similar for every type. Review the entrance process as part of practicing each transition type.
Exception: The Boot to Skin transition doesn't require you to unzip your suit. Your skins stay on your skis when booting, so they're already where they need to be.
Exception: If you're accustomed to approaching with your poles in your left hand, the boot-to-skin transition should be the exception (to do it with your right.) Ski hooks are located on the right-hand side of packs, so putting your poles down with your right hand will set you up better to unhook your skis with your left.
This exception could also be a good argument for having your approach hand always be your right for every transition.
The tip of the ski hook will be pointing to your left-hand side. Because of that, it's easier to pop the hook with your left hand than it is with your right.
Also, because the ski holster is on the left-hand side of most packs, you can grab your skis with your left hand and remove them in one motion.
With the ski hook popped, let your left arm "unroll" in front of you. It'll feel awkward for your wrist at first. The end position is the same one you started in when you holstered your skis. Your palm will be up and your thumb will be pointing outward.
The following video breaks down the Boot to Skin skimo transition according to the above instructions.
The Boot to Skin skimo transition
What if the bootpack ends at a ridge top or couloir?
Keeping your skins on through a bootpack section makes your skis easier to manage at the next transition when putting them on the ground. With skins on, your skis are less likely to slide away from you and possibly ruin your race if they head downhill without you.
And you don't lose any time by moving the rips to the top of the bootpack instead of the bottom.