I used dish soap for this, then dried, then sprayed with isopropyl alcohol and wiped with a microfiber cloth.
Let glass dry completely
Mix formulation, then heat to melt.
I used a microwave for this for speed, but a stovetop burner works fine as well.
While gelatin is still hot and liquid, pour gelatin on glass surface and quickly tilt the glass around to spread the gelatin evenly across the surface. this will be messy! you will spill! be prepared
the gelatin cools pretty rapidly at this point, so you do need to be fast.
once the glass plate has been coated, let it dry & harden. Exact time tbd, roughly a few hours.
coat with sensitizer, let sensitizer dry, then expose.