A flat surface around the bed of your sewing machine can make the difference between struggling with quilting and quilting with ease. Here’s one way to achieve that custom surface with some construction rigid foam insulation and a piece of flexible clear vinyl. I have also seen a blog where a quilter used this method, but set her sewing machine perpendicular to her body (needle close to her and motor farthest away). No matter what system you use, you will find that you are more comfortable and your machine quilting is easier with a flat surface for the quilt to lay on while you are quilting it.
Here’s how to adjust it for machine quilting a large quilt.
Here is a full write-up of the process as well.