The key to a successful transition is not unlike trying to root cuttings directly in soil. It requires a soilless, peat-based, porous potting mix with added perlite and a small pot. The porous potting mix and small pot will help maintain the even dampness around the roots. Of course, you will have to monitor the soil moisture carefully, especially in the early stages.
The plastic bag is unnecessary as long as you monitor the soil moisture carefully.