Hi Grace,
You can spray your quilt sandwich with basing spray, there are several kinds available, and the quilt in the ditch, or even across the diagonal. I have a couple of patterns that I have used that I quilted across the diagonal with first a regular straight stitch, using a walking foot, and after I got my new machine I used a fancy stitch without the walking foot. There have been a couple of good threads on here lately about spray-basting, everyone's preference and how to best do it. After I baste mine, if I am quilting on the diag, I frequently will use cheap narrow masking tape and mark the quilting lines on one direction, then roll the quilt from either side leaving a tape line in the approximate middle to start the quilting, just unroll from one side and reroll on the other until you go across the first half of the quilt. I then will put in on the floor and reroll the quilted side nice and tight and start over with the other side. I have made about a dozen queen size quilts and have quilted them on my regular sewing machines.