So here the tutorial how I made it.
You'll need very thin needle. I used needle for beading for smallest beads. If you find it hard to stitch with this needle for the start you can use the regular one. I stabbed my fingers with it, it is not the funniest thing.
Hide it beneath your next stitches:
Stitch all pattern or before you have 10 cm thread. If you use regular needle it is time to cut the thread near eye of needle and take the thin one.
Very carefully thread the needle under few stitches:
Extend the needle and all thread:
And cut the thread carefully near the stitch:
Now your front and back sides looked perfect:
And here is finished design:
Good luck with crafting!