I wash my quilt after quilting but before binding. The fabrics set and I can then lay it on the floor to dry. Make sure the lines are staight and it lays perfectly. If you have a carpet you can use T-pins to tack it down. If no carpet, I use something heavy on the corners. When dry I then square it and bind it. The ones I have not washed were not so well squared after they were washed. Also the quilting marking lines will go away, since I use a water soluble marker.
Maria