Step 1: Create the mold - 1
Then, you must create a mold layout. With the masking plate down, I laid out all of my mini figs. They will shake around a little bit from the platform going down and up. I might try attaching them to a large, flat lego surface, but you must be careful to not cover the vacuum intake. It worked pretty well without that, though. Keep them away from the edge by about an inch.
Then, lower the tray. Since they are plastic, I lowered it quite a bit to make sure that I didn't melt them.