Tony

After reading your post again I think your plan is to keep the horizontal section of trunk and induce roots to grow there. If so, you won't need to layer it completely but the procedure is much the same. You could either strip a section of bark or nick it with a knife all along where you want roots to grow. Treat that area with rooting hormone and pack some sphagnum moss around it. You may need to lower the planting depth to do this, if so that's not a problem. Keep it outside in good light and don't let it dry out and you should have new roots in a couple of years. It will need good winter protection for the first few winters, if you're in a cold climate.

Tony