Finally the first seam (partial seam) can be fully closed. Done! And know what? You can do the trick on paper too! Just lift the designated part of the second seam from the foundation paper. This gives you room to join the first strip properly.
But anyhow - no matter whether you sew with or without a foundation: The technique is limited by the size of the pieces. When the pieces are too small the process will get fiddly.