If you don't want to make this a pain in the keister, then you need to think about how to set up to make sabots easily...meaning with as little time consuming labor as possible.
A sabot is nothing more than a device used which will enable your cannon to fire a projectile with a smaller diameter than the bore. Making something that will enable you to create sabots for a variety of different diameter core projectiles with little effort should be your goal. Once you have that, you'll be good to go to create sabots for whatever you want to fire.
I have a carbide cannon with a three inch PVC bore, so I've given some thought to this. At least, I did before finding oversized tennnis balls that perfectly fit the bore. Here's how I would have gone about it:
First thing you need to do is make a mold with an inside diameter that matches that of your bore. Actually, you may need to make the mold with an inside diameter that is slightly smaller than your bore. This doesn't have to be anything too fancy, but it should be durable because you don't want it falling apart after making only one or two sabots.
The mold should have a hole in the bottom. The purpose of the hole is, at the minimum, to allow you to push your completed sabot out of the mold. An additional function of the hole would be to allow you to properly center and support the core of your sabot inside the mold without any extra support required. This would be accomplished by sizing one end of the core of your sabot to fit the hole enough to allow the core to stand on it's own, properly centered in the mold.
Once you've created your mold, spray the inside with something like a silicone lubricant. Place the mold on a level surface and insert the core of your sabot. Now pour a "potting compound" of your choice into the mold. This can be a plastidip, plastisol, epoxy compound, fiberglass, or any other substance which you can mix and pour around the core. The key is that it will bond to the core and set up/harden while sitting in the mold.
Once the potting compound has set, pop your completed sabot out of the mold. (This is where the hole in the bottom comes in handy.)
After some experimentation on what works best for you in terms of the mold and potting compound, you can now make several more molds so you can make more than one sabot at a time. If it takes a couple hours for the chosen potting compound to set up, it would take quite a bit of time to churn out a dozen sabots. Make a dozen molds and you can then make several dozen sabots on a lazy day.
There is a large variety of materials you can make a mold from, and even more materials you can use for the cores and potting compounds. For example, plaster of paris might make an interesting sabot because it may hold together just long enough to perform it's primary function, yet essentially be pulverized to give a more dramatic "smoke" cloud as the round exits the barrel.
If you make your mold out of a fairly rigid, but slightly flexible, material (like some plastics), then the slight flexibility may make it easier to pop your completed sabot out. Likewise, making the mold out of metal might give you the ability to heat the mold with a hair dryer to cause it to expand slightly, making it easier to pop the sabot out.