I like to tape mine to the vinyl flooring in my kitchen. It has nice squares to line up the back on. I put masking tape on several places along all the edges. I put a pin in the tape/fabric edge to hold it better and the tape sticks well to the vinyl floor. You can get it nice and flat and then proceed with the rest of the sandwich. It also helps to iron and starch your back before starting. I do wear the velcro padded knee protectors for crawling around the floor on and have a kitchen chair close to get back up with. I look at it as my exercise class for the day.
If I'm going to use fusible batting I use the old carpet to pin and iron my sandwich on.