Note - I'm working under bad lighting for the photo so the colour in real light will be a lot brighter
Using another ceramic bowl pour out some of your glass balls (all sizes if you have them) and mix in some of the coloured liquid fimo from your other bowl (picture above).
When all mixed and all the balls are coated pour this into your cauldron (picture below). Fill up to just below the rim. You may need to use a cocktal stick to prod and push the balls around, Now bake in the oven for around half an hour as to your fimo and liquid fimo instructions.
Next stage coming up shortly - will make the bubbles spill over.