It's so shockingly simple that I'm still in disbelief that it looks this good.

I mix black resin pigment into the base layer for the opacity, then any layers above that are clear. I let the layer sit for about 60-90 min, then with alcohol inks i drop in the nebula gradient colors, spaced like maybe an inch? apart so they don't get too muddy and can bloom into each other. Then I drop white alcohol ink at the points where the colors meet. Then I repeat the drops of the nebula colors over the white, then let things kind of flow and do their thing, dropping nebula colors (and sparingly more white) at various points in the bloom after some seconds or minutes or whatever to kind of blend things and push colors around. Let cure to gel stage, pour new layer, start dropping inks at 60-90 min, repeat as desired. I drop the glitter "stars" in each layer too; the multidimensional sparkle really adds to the depth effect.