Bury the plant about an inch below where the roots emerge, and gently pull the plant upward to the right level after back filling.
If your substrate is within a good grain size, plant any stem plants by making a small hole with your fingertip, plant, and back fill with substrate. Bury the plant about an inch below where the roots emerge, and gently pull the plant upward to the right level after back filling. This will let the roots orient themselves a little better.