Reddit mentions of The Lockback Knife: From first Design to Completed Folding

I think you'll find that there is more material out there for slipjoints than lockbacks, but there is some stuff. Here is a decent list of folding knife work-in-progress posts and tutorials on the Knife Dogs forums. It has tons of tutorials and WIPs, for folders of all kinds as well as fixed blades and just general knifemaking techniques. I also have this book, which is very good. One more option would be to buy a lockback kit from a knifemaker supply shop, like USA Knifemaker and copy the pattern or something.