Here are two pink square knot drizzle stitches and a drizzle stitch between them. I used perle 12, a milliners needle and I stretched the fabric in an embroidery hoop. For this tutorial I used 2 different colours. That way it was easy to see how I made this stitch and it yields a nice variation with two different sides! This stitch is not difficult if you are familiar with drizzle stitches.
Bring 2 threads up through the fabric and unthread the needle, just like you would do with a normal drizzle stitch. Put the needle back into the fabric slightly above the point you came up and secure the needle by bringing it up a bit further. Bring one thread to the left side of your needle, the other to the right side.
Take the thread on the left side and make a loop over your needle.
Take the thread at the right side and take it over the looped thread, under the needle and through the loop from the back to the front.
Pull both threads gently at the same time to make the first half of your knot.
Take the thread on the right side and make a loop over the needle.
Take the thread at the left side and take it over the looped thread, under the needle and through the loop from the back to the front.
Pull both threads gently at the same time to make the second half of your knot.
Continue making knots until you have the size you want. You always make the loop at the side you see the last loop on top. If you look at this picture, you would make the loop at the left side.
Bring your needle carefully upright again and thread it with both threads. Hold the knots between your fingers and pull the needle through the fabric. Pull the threads through the knots.
This is how it looks on one side.
And this is the other side!
Two more variations. The one at the left side has a bead at the top. I did this by adding it to the threads with a second needle before I made the last step of this stitch. The one on the right leaning forward is a half square knot variation. If you make the first half of this stitch only, it will twist. If you make the second half of this stitch only, it will twist the other way!