Mark the mouth on the face with erasable fabric marker. The shape is rounded corner rectangular, with bottom align to the face’s border and top covers a little on the felt eye.
Fold and baste the raw edge of the mouth, then pin it in place. Slip stitch around until you are about 1″ away from the starting point.
Stuff the mouth fully. Continue to slip stitch to the starting point to complete the mouth.
Embroidery branch stitches across the middle of the mouth. Tips: look out for the toe seam line of the sock, this is where the middle is.