How do I create and lock a single photo album in ios10?
You can't lock the photos, but you can hide them.
Hiding photos is a simple enough process. Start by opening up photos and selecting all the photos you wish to hide.
Now, click the share button and scroll through the bottom section looking for an item labeled 'Hide'.
Now, the only place that the photos are accessible is in Photos &gt; Albums &gt; Hidden. There's not even a preview so the photos stay extra hidden.

Unfortunately, there's no native (as you requested) way to lock these photos with a PIN, but now the only way to see them is to find the Hidden album.
All photos in the Hidden album are not shown in Moments, Collections, and Years. Until iOS 11 and macOS 10.13 High Sierra, Hidden items will still appear in auto-generated albums, like selfies, screenshots, etc.