Better post up a photo of the plant in question. When a slipper orchid is truly large enough to divide, it two presents an easy way to divide. You want to be careful to not divide a plant that is too young. Slipper orchids use the old growth that has bloomed before as a food source for the developing new growth. If you divide and take away the food source, you will likely not get blooms for quite some time.
cheers,
BD