Making soap balls for the use of embedding in a log of soap is commonly done. I've done single color soap balls, complicated layered balls, tiny and large. This creation is talking about rainbow color soap balls and how I made them.
I started with making a batch of fresh soap mixed with each individual rainbow color. I usually unmold the soap and wait for 2 days, that's when my soap is still soft enough to knead but not sticky anymore. Then I kneaded each soap dough into thin long rods.
Combined the rods, cut into sections then twisted them into balls. It is time consuming but look how pretty those balls are! Usually if I want to embed big balls into a fresh batch of soap I need to do it within a week, otherwise the balls will get dried and become too hard to cut against soft fresh soap. Here's the final soap I used these balls in: