Skin to Boot
Bootpacks are too steep to skin, so racers must switch from skinning to booting. With practice, a bootpack transition can be done in a few seconds.
With enough practice with the right gear, a ski-to-skin transition can be done in less than 10 seconds. 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 Skin to Boot transition doesn't require you to unzip your suit. Your skins stay on your skis, so there's no need to open your suit.

Use both hands to press down on both toe pieces almost simultaneously. (You'll need to switch your weight from foot to foot to get out of your bindings, but the switch should be very close together.)
Fall to one knee with your skis between your legs. (Doing the skin-to-boot transition on one knee, eliminates the extra standing and kneeling movements of trying to do it standing.)

Grab your skis and turn them so that they are base-to-base. Use the ground to align them. Offset your skis so that the right-hand ski base is exposed.
Offsetting the bases will make it easier to eyeball the tails into the ski holster on your pack. Without the offset, it's not uncommon to miss the holster with one ski.