Usually cut batting larger than the front, same for the backing. About 2 inches all around. They seem to shrink a bit when you quilt them together. Folding the back over to the front is definitely a way to finish it. But, that is not called bias. The fabric used from the back is definitely on the straight of grain. Check some YouTube videos if you feel you need more help. They are great. You must quilt it by tying or stitching before you bind the edges.