Here's how you clamp the workpiece in the jig. I'm watching to be sure the scribed baseline is aligned with the top of the jig. My left index finger is holding the sliding clamp tight, my left pinky is holding the workpiece so it doesn't slide, and my right hand is tightening the clamp's screw.
The loaded jig clamped into my bench vise. A sacrificial back board prevents blowout at the end of the cut. Unlike typical paring setups, this one lets the chisel be horizontal. It's quite easy to use the jig while seated on a stool, a real benefit if your back ever hurts.
Using my narrowest chisel, 1/8 inch, to establish a narrow area pared to final depth. Notice how simple it is to hold the chisel flat against the plastic surface, which is hard and slippery. Chisels used with this jig need flat backs!