This is sometimes called "parfait" dyeing (layering fabric/ice/dye). I cut my fabric into fat quarters so I have eight pieces. I am only dyeing 6 of them this way.
I soaked my fabric in water with soda ash for about an hour.
I am using a large enamel pot, and put an enamel strainer in the bottom. As the ice melts, I don't want the fabric to sit in the puddle of water in the bottom of the pot. The strainer is about 1 1/2" high.
I squish my fabric so it fits in my enamel pot.
I then add a layer of ice.
I sprinkled Procion MX dye powder on top, three colors and less than a teaspoon of each. I then did another layer of fabric/ice/dye powder. The first pot I only got two layers. The second pot, I got three layers.
I threw in a piece of sheer that I was pretty sure was polyester. Sure enough, it didn't dye.