Batting shrinkage in rag quilt

I just made my second rag quilt. I wasn't thinking and tutorials, which are numerous didn't point out the obvious, and my warm and natural batting shrunk leaving areas where the quilt is just the top and backing. In other words, it pulled back from the side seam toward the x in the center of the square.

The obvious solution would be to 'catch' the batting in the side seams so that it won't pull back when it shrinks. But I am not convinced that 'just barely' snagging the batting in the side seams will be enough for a quilt which will eventually be washed numerous times as it's a baby quilt.

Numerous tutorials say cut the batting an inch smaller than your squares, sew the x, and then piece your blocks together with 1/2" seams. If that is the norm than people everywhere have shoddy, lumpy quilts.

So, what is the consensus? Cut the batting larger? Sew around each block before piecing them all together?

Also, do most preshrink the fabric?