There is a method called the pillow turn, where you layer the top fabric down on the backing and the batting, sew around 3 sides and leaving a space to turn in the 4th seam. Then you turn it and hand stitch the seam closed.
I don't like that method because I have a hard time keeping everything straight. My result has been wonky or skewed.
Now, I do a standard sandwich. Lay the background fabric on a flat surface WRONG SIDE UP (I tape mine down so it is nice and taut). I lay the batting on the backing smoothing it nice and flat. Now I put the top on - PATTERN SIDE UP again smoothing the top down flat.
Many people pin baste (I pin baste about hand width apart). Some people baste with long basting stitches.
Then you quilt the quilt. Finally, add the binding and you are done. Easy breezy - right?