It is usually easy to see the original depth that a plant grew at. Just look for the lighter area of the leaf at the base of the plant. Place the plant at that depth in a new pot, and firm the soil around the base (it doesn't matter much if it has roots or not at this point). I will usually add a couple of stakes around the edge of the pot and tie unrooted plants to them until they stabilize. I always top off with .5" of rock or gravel on top of the newly potted plants. Don't water too much (you don't want to rot any roots before they can get started), and wait for the plant to grow.

I've noticed that I have better luck rooting Sansevieria when I start in VERY small pots (just large enough to hold the base of the plant). Once I get roots filling the small pot, I move up one pot size at a time until the plant is in a large enough pot. I did this with a S. masoniana cutting that was 24" tall. I started it in a 2" pot (the rhizome just fit), and repotted it every month until it sent out its first new shoot. I had to put it in a 6" pot at that point, as the rhizome was that big, and very thick. It filled the 6" pot with roots, and sent out the shoot in 6 months from reciept. The plant has pretty much been repotted yearly since then. Other plants that were started in 6" pots seemed to take over a year to fill the pot with roots and send out shoots.

Joe just gave you the straight scoop on that. Didn't want you to think that no one else wanted to answer your question, but there isn't much more to say!

Over-watering will be your biggest challenge until roots form. I often use a mister and just mist heavily when I feel I should be watering. One of those plant person urges I work hard to overcome!

Good luck with your new plants, and hope they take hold quickly. Winter is not always the best time for establishing new plants.