Place your circular saw with the sled attached on the newly mounted aluminum angle.
Lower the saw until the blade is at the correct depth.
Start the saw and make the cut along the hardboard.
This cut represents the inside cut edge of the jig, thus, anytime you make a cut using the jig, line the edge of your jig up with the lines marked on your sheets.
Now you can run the saw, still attached to the sled on the opposite side to cut the jig away from the rest of the hardboard.