I cover my king bed with a big flannel sheet and spray baste. The flannel sheet holds the project in place and protects from over spray. Trick to spray basting is to start lightly and increase according to need. Some projects take to the spray better than others. Doing it on the bed saves the knees and back and spray basting a king quilt can be done in less than an hour.
I also routinely quilt large quilts on my 9" Janome, but have done them on smaller machines. All but one of my 151 quilts have been done by me on the domestics. It takes practice and patience. Just finished one 108x108, another 96x104, and one 108x120. Some are done straight line diagonal, some SID, echo and shadow quilting, and most have at least some FMQ.
I started out with small quilts and slowly got the confidence to do larger ones so don't get discouraged. Like I said, it takes practice and patience. My first attempt at FMQ is embarrassing and I wish that quilt was not being used by a grand niece!!
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This is the 108x108 and it has several different quilting designs and techniques.