I generally use a bed, too, and since I've found spray basting gets all over everything in a room, I pin baste. I have a few older cutting mats that I shuffle underneath the quilt. I am very careful about getting the back of the quilt to lie flat before adding the batting and top. This can all be hard on the back, so I take frequent breaks or sit on a chair to work my way around.
Alternatively, I quilt full-sized and larger quilts in sections and also pin baste on a big meeting table at our historical building. It and our public library aren't open right now due to covid, but the library is another possibility when it reopens.