I love John Flynn’s method of making a quilt back (it’s about halfway down the page on the link). It uses less fabric, and avoids a straight seam in the center of a quilt, which is a pain when trying to longarm. He has a PDF to calculate the yardage needed,and if you suck at math like I do, he’s also got a great app that figures out the calculation for you – well worth the $1.99. But instructions on exactly how to do this were nowhere to be found. When I made my Australia t-shirt quilt I used this method for the backing, and remembered to take pictures of how I did it. Hopefully this will help some others who are trying it out for the first time. A couple of tips: Having a helper will make this process SO much easier. Trying to do the diagonal fold by myself was quite taxing! Also, look at the selvage of the fabric you’re considering. If the selvage edge is quite thick with no print on it, reduce your width of fabric in your calculation. You don’t want to end up with selvage in your quilt!
Step One: Take your full length of fabric and fold it diagonally from corner to corner.
Step Two: Cut along the diagonal fold. This is the scariest part. That’s a LOT of fabric to cut, and you’re thinking “No way can this work!” and how you’re gonna kick yourself in the arse if it doesn’t because that’s a lot of money you just spent on this backing. But take a deep breath and just CUT. If your calculations were correct when you bought the fabric, this will work. Cut the fabric!
Step Four: Skooch the fabric. Move one side down and you’ll see the backing magically get wider. Once again, two people make this job SO much easier!
Step Five. Carefully lay your quilt on top of the fabric, and keep skooching and checking until the backing completely shows underneath the quilt. And remember, you’re going to lose 1/2″ in your seam allowance, so be sure to allow for that. Since I longarm my quilts I needed extra backing area, so I adjusted my backing to give me the four extra inches on each side that I’d need.