Some blocks seem to be easy peasy - until you start sewing. In this case wherever you start sewing you will end up sewing fabric to air. You need a trick that is called "Partial Seam".
This is how to do it:

Place your first strip right sides together onto the square. Sew only a part (~2") of the seam starting at the edge where both pieces align. Backstitch. Press.

Now it is easy to add strips three to four as usual.

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.