Plectranthus amboinicus is a member of the mint family and as such, rather willing to spread and be propagated.
The most common method are stem cuttings, which can be rooted either in water or put directly into soil.
From the tips of the plant, cut short cuttings that are between three and five pairs of leaves long. Remove the bottom pair or two, then you have two options:
- Plant the cuttings directly into damp potting soil.
- Let the cuttings root in a jar of water for a few days and plant when the roots are a few cm or a scant inch long.
As for all cuttings, don’t put them into direct sunlight because they have no roots yet. Lots of indirect light is perfect. And if you have a mother plant that needs trimming anyway, I suggest making multiple cuttings, so it won’t matter if some fail. You can always choose the strongest ones to keep or give away the surplus.