If the whole stem is leaning I would be careful and even avoid pulling the stem back to a stake. They can easily break off at the bulb. For those types I scrounge around for my plastic lawn chairs and let them lean on the back of the chair for the season. I usually have to use horticultural tape to keep them from sliding off the back of the chair. Put a pot of flowers on the chair seat to hold the chair in place.
If you have a kazilion lilies like this then it is obviously impractical.
