Okey!
I set up an glass vase with AquaSoil Amazonia (from my planted tank) och the same ammount of vermucilit on the top. Then I just stuck the Cryptocoryne down in the substrate. I filled up with water up to the top of the highest substrate-level. Then I also put some plastics over so it shouldn't dry out. I will make some holes in the plastic in some time, when the plant have growned out some emersed leaves. Probably I will be able to have this vase outdoor in the summer! This is what it looks like now:
I also placed some moss from my planted tank in the vase.
Please give me some feedback on what I shall do or change!