Etiquette for sitting on a zabuton includes not standing on the zabuton, and first of all kneel on the zabuton on the side away from the seat of honor and use one's knees to pivot 45 degrees in the direction of the zabuton.
座る側の作法としては、座布団を足で踏まず、まず座布団の下座側に跪座し、膝を生かして座布団の方へ45度体を向きかえる。