Having unfortunately purchased this piece, I would say, don’t play it at all. It doesn’t even meet the basic requirements of a composition, a sense of line, a real theme, good form. I don’t know how it got chosen. While all new music should theoretically get played, “tonal” music can be just as bad as “avant-garde.” But, I guess you’re stuck with it. You are free to choose, but he would seem to have implied only the first chord should be flat, but I would assume it continues if the chords are similar. I always err for consistency within a phrase.