I use an embroidery hoop to work on mine. Either one as big as the whole square or one smaller, personal preference. A big hoop may be hard to handle. But either will keep things taut while you are trying to stitch. My dresden plate pieces were sewn together on the machine before sttiching to the background, but the dahalia one that I am working on now is stitched directly to the background because the pieces overlap each other to form the design.
Maybe this will help you a little. I use a back stitch and and just slip my needle under the edge of the piece, catching the background fabric at the same time, so that the stitches won't show. I can do it but explaining it with just words is hard! Hope this is clearer than mud! :lol: