I haven’t worked with this resin. It sounds like it may not have enough surface tension to want to stay even on the surface. I would suggest using a thicker mixing (doming) resin. If this is a doming resin, you may need to create a tape dam around your canvas. Pour the resin, then remove the tape after casting.
Are you using anything with an oil base on your canvas? The resin won’t want to stick to that either which can cause the fish eyes.