This isn't an exact answer to your question, but I recently embroidered a Halloween sampler. The pattern had you put a layer of muslin, cut same size, behind the piece as it was worked. It helps to hide thread tails and traveling thread when the piece is completed. It turned out very nicely.
I did baste the 2 pieces through the center and around the outside. You could baste more if the piece is very large.
kathyd