I just finish a fairly large wall hanging quilt and free formed all over the place, learning a great deal in the process. Start at one side and work over to the other, but don't leave anything to go back to in the middle. (that was my mistake) Or, start in the center and work your way out. Don't work from the outsides in, as the fabric will bunch up and you won't be able to get it flattened out as you quilt.
M