The first stitch is a single herringbone and then filled in the curve with closed herringbone making bigger stitches on the outside curve. I suggest you draw the shape/curve you want onto the fabric. It is quick and easy to do and can be used 'as is' or add extra stitches and beads for a CQ block.
Pumora's embroidery stitch-lexicon: the woven bar
COMO SACO EL TAMAÑO DE UN DIBUJO? PUES CON UNA REGLA DE TRES - UNA VEZ IMPRIMIDO EL DIBUJO se lo que mide sobre un folio, mido mi tela y saco la proporción
embroidery tutorials: backstitch with variations bordado, ricamo, broderie, sticken
Nostalgia at The Stone House - My Creations: Buttons and Bags