Curtis (MesquiteMan) has plans on his web site showing how to make a mold and a mold caddy (to hold/steady the mold in the pressure pot). They're both no cost....
He has some tutorials posted there that link to his YouTube tutorials on using a pressure pot.
My pot is strictly for pressure work. I have a vacuum chamber for stabilizing. That simplifies the attachments needed on top of the paint pot...
You need the pressure regulator, pop-off valve, pressure gauge, ball valve, and a connector that will mate with your compressor's hose fitting. Inside the pot, it's worth adding a 90 degree turn to the air flow so it can't blast down into your liquid resin when you start pressurizing.
If you only fill one mold at a time, and make the caddy like Curtis shows, there will be a wooden layer blocking any incoming air so you can skip the 90 degree elbow under the lid if the slight cost is really a problem.
You might also want to make a much smaller mold when you're first starting. You'll get the colors wrong, get the swirling wrong, and make a variety of other mistakes. Smaller blocks mean each screw up costs less (and wastes less material).