Take small stitches in a brick pattern over two of the diagonal threads as shown. This takes a bit of practise, but is not difficult.
Center of flower is executed with this stitch. It has also been padded heavily with course cotton thread similar to worsted weight yarn.
A similar stitch. Threads are laid horizontally. Small stitches are placed every sixth stitch of the ground threads over one thread only. Each row is alternated to form a brick pattern. It can also be stitched as the diagonal pattern in example one above, over two horizontal rows.