Since my Unisaw doesn't drop a 10" blade completely below the bottom of a new ZCI, I usually begin the cut by putting a 7 1/2" blade on the saw. Then I clamp a scrap of 2 by lumber to the fence and position this scrap wood next to the blade location and very close to where the blade will come up through the ZCI to hold the ZCI down while I raise the blade up through the ZCI. Then I start the saw and slowly raise the blade. Once up up through the ZCI. The blade is then lowered and the saw turned off. I then replace the 7 1/2" blade with the desired 10" blade, and repeat the process of turning the saw on and slowly raising the blade, but this time raising it to as high as I think I will ever use it. Then I again lower the blade and turn the saw off. I then get the correct Allen Wrench and level the ZCI with the 4 set screws that I have previously installed in the ZCI. I then remove the ZCI and write on the bottom of it which blade I have made it for.
I always use the same blade with it's mating ZCI, so as not to have the slot any wider than that particular blade. This is why I have about a dozen in the drawer next to the saw at any given time. I also keep several blank ZCI's that I've previously made in the drawer, so I always have a new one ready in case I buy a new blade or decide that one of the blades has damaged it's mating ZCI, so I can replace it quickly. Whenever I find that I only have a couple of blanks left, I make time soon after to find some suitable scrap and make about 6 new ones to put in the drawer. I never want to be completely out of ready-to-use blank ZCIs. Most of my shop made ZCIs have been made from Corian counter top sink hole scrap or 12 mm Baltic Birch.
I don't think I've ever made any from Lexan, but it should work fine. Just use the fence, a clamp, and a scrap of 2 by wood to hold the ZCI down while you cut the blade slot in it. Use a smaller diameter blade to start the slot if the lowest position of your blade still touches the bottom of the blank ZCI.
I just came into a deal to buy some phenolic blank ZCIs for my Unisaw and bought 8 of them for $5 each, So I doubt that I'll be making any myself for a while They even came with the height adjusting set screws.
Central North Carolina