I do what I've heard called 'birth' a quilt...I think that's what you're trying to do. Sewing all the way around = leave a good opening and turn it right side out and then top stitch around the border.
I leave my batting and backing larger than my quilt top. The top is truly square. I layer it just like a regular quilt by taping it 'taunt' to the table and then pin the heck out of it - both in area of the quilt top and along the edge.
I have 2 waiting to be sewn right now. If you'd like to see a picture of my pinning - let me know.