Although I don't use many precuts, I usually don't prewash for fear of fraying and shrinking out of shape to be usable. However, I have pre washed some Fat Quarters that I was worried about bleeding dye, and I just put them in a sink of medium hot water, let them soak for 10-15 minutes, then gently hung up on hangars with clothespins to dry. No agitation or tumbling in dry to avoid fraying.