It's A Wet Heat...
Hi,
L. Aromatica is easy to transition from immersed to emerged or round the other way. The emerged version requires high humidity and likes heat.
I like two-liter plastic soda bottles for the purpose. However, plastic bags over various containers work well.

I have a bunch of stuff growing in resalable bags.
I top cut six inches (15 cm) off a stem and cut on the bias into three segments is a nice amount for a two-liter bottle. Technically, I think any section with at least three healthy leaves ought to grow.
Since L. Aromatica is an herb, I suppose root hormone approved for plants intended for human consumption should work, I have not used it for L. Aromatica.
I plant the stems in enriched soil, violet potting soil, worm poop, Miracle grow whatever is handy, I think it is nice to cover the substrate with gravel. Aquarium water from an established planted tank, either to the top of the substrate or to just covering the plants.
Place the containers in a bright warm area. These plants like heat, they like light, they grow like crazy, nice flowers as well.
Biollante