You can sub glass with gelatin, or just coat the emulsion directly on the glass.

The trick is to clean it well of all grease and oil, don't leave fingerprints, and harden with chrome alum.

There are other comments and some photos of how this is done posted in the emulsion making and coating forum.

Also, please be aware of the fact that all of these emulsions must be refrigerated, not frozen nor kept at room temperature, or they will not keep well. Also, every time you warm up the bottle to get some out, it changes slightly due to the heat cycle. That is why I store my emulsions in wide mouth containers and rather than re-heat them, I scoop out my sample with a spoon or a spatula.