I would get a length of material and sew right sides together and then turn it right sides out and close off the end. This is the way I do my blankets.

I use fusible interfacing ironed onto the back. It also keeps your stitches `locked`into place in case you need to wash it.

I use heavy, qualitative fabric and try to do extra clean work. I place the item in a garment bag and wash on the gentle cycle. So far I haven't had a problem. Fusible lining can cause puckering in some cases. I buy finished runners and toppers, so lining, as ella suggested, wouldn't work.

The reason I mentioned buying heavy fabric is that there is less of a chance of booboos showing. I took lessons on how to anchor floss and it made a huge difference. I'm sure that tutorials are available. I have also bought many books on embroidery and although they go into great detail on how to work the various stitches they never explain how to anchor floss. So annoying.

Nobody will flip your runner over to see what it looks like, so don't worry. Instead proudly display and enjoy it.