I think this guide mean L button and spring instead of ZL button since that is attached to the mid frame which was removed before this step.

When resembling make sure you are patient and careful with this step. It's pretty finicky and you'll to try a few different ways of getting it on. Have a Zen approach.

Just like everyone else I recommend skipping to step 21. You don't need to take all the components out to replace the circle pad.