Chop the glycerin soap into smaller chunks. Place in a microwave safe container and pour in the activated charcoal.
Microwave the glycerin soap until melted (only takes slightly over a minute in my microwave). Mix well, until all the activated charcoal is fully dissolved. Pour into molds slowly until nearly at the top of each cavity.
Allow to completely cool (yes, it is fine to carefully place them in refrigerator), then pop out of molds.
Before pouring your soap into molds:
If you are using pigment powder, take a toothpick and scoop up a tiny amount. Fleck into the soap mold cavities in a random pattern. Keep it in tiny clumps.
Sprinkle glitter in the soap molds. Lighter tones of blues and greens are my favorite as they contrast nicely against the black of the charcoal soap. Use 2-3 complementary colors in each cavity.
Finish as above.
I used half frankincense and half orange essential oils in the plain soap and just lavender in the Galaxy soap version.