That's not quite how I lay mine. I put batting down first and smooth it
flat. If there are any wrinkles or waves in the batt, I get them taken care
of with the steam iron. Don't touch the iron down on the batt. Trust me. I
like for the batt to be an inch or two larger than the backing. I smooth the
backing out flat on the batting with the backing face up.
Then I put the quilt top on top, face down. This lets me be fairly sure
that the batt and backing haven't traveled off in any direction. If batting
and backing are a little larger than the quilt top, it helps. You can trim
the excess off after stitching.
Worth repeating: don't forget to make an "X" with pins at the beginning
and ending of the opening you want to leave for turning. IF you forget, you
will remember next time. Polly

"Sharon Harper" wrote You could - but didn't you sew the batting "in"
with the back and the top?
You know - backing right side up, top right side down, batting anyway up,
sew around the edges and twist yourself inside out?