What I developed for closing a lockback one-handed is the following:

1) Hold the knife tip down with your thumb on the lock on the back and the BACK of the blade near your leg.
2) Use your thumb to unlock the blade.
3) Start the blade closing by pressing the back of the blade against your leg.
4) As the blade starts to close, move your fingers to the sides of the handles.

This is NOT a technique to be hurried. Leads to bleeding and bad language.

For people who are nervous about fingers and blades, I have them hold the blade securely, unlock the lock, and fold the handle toward the blade. Control of the blade is better since it is always gripped.