How important is the size of my backing?

Very!!  Please make sure I have at least 3" extra on BOTH the sides.  I like the backing to be as flat as possible so I use a tool on the sides that keeps a constant, gentle pull on the sides of the backing.  That being said, too much extra on the sides can cause other issues when rolling the quilt, so more than 8" each side isn't necessarily better.  I will have to trim the sides down.

Now, the top and bottom need to be at least 3" extra on both.  More fabric on the top and bottom is okay.  The backing needs to be square. If I have to square up the backing (and squaring up the backing is so important!) and don't have enough fabric on the top and bottom it is a huge issue.  I won't be able to quilt your quilt until I can get a new backing from you.  Frustrating.  If I need to sew fabric to the sides to have enough, I will charge for my time and materials.

Yes, piecing your backing is fine.  I generally piece mine and add leftover fabrics and blocks to mine.  Just make sure I have enough and it's squared up.

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(The back of my Alison Glass Alternative quilt.  It is pieced with Tula Pink's True Colors fabric and a strip of Alison Glass' Ex Libris fabric.)

How best to piece?  Well, if your quilt top is 54" x 72", buy 3 1/2 yards (126 inches).  Cut the yardage into two equal pieces of 1 3/4 yards (63 inches).  Pin the selvage of the two pieces of fabric right sides together with directional prints going in the same direction.  Using a stitch length of 2 mm, sew 1/2" away from the selvage.  Trim the selvage off.  Press the seam either open or to one side and press the entire piece of backing which should be approximately 63" x 84".  If you don't feel comfortable squaring your backing up at this point, let me know and I will do it.  

To square the backing up, take the two selvages (top and bottom of the backing) and match them together by folding the backing in the middle.  Watch for any bunching along the fold/seam.  Move the selvage until the fold lies straight.  Using a large square ruler and the lines on your cutting mat, line the folded piece up and cut the sides even and square with the top and bottom.  Again, if you don't feel comfortable doing this, let me know and I can do it.

I do have several 108" backings in stock if you would like me to provide your backing.  I will post pictures and prices per yard in a later post.

Piece out, Julie