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As I see it, a tea towel is a utility item and as such, can be more casual than an item made for show or competition. Embroidering as neatly as possible is good, but I wouldn't worry too much about the back side. I LOVE hand embroidery and have many items from my sister, who does a neat job, but no covering on the back. I always fold them with the finished side out and hang them that way, too. So, to me, it the back really doesn't matter.
I love this board, thank you so much for all the tips and pics, i was taught to embroider by my 5th grade teacher, and have always loved to do it, have lots of flour sack towels and thread, and lots of surgeries so will be doing lots of these. thank you again
Mary