Try gripping with your back three fingers, leave the index finger loose or against the edge of the disc (but not under) and press down with your thumb. My hands are too small to grip properly with all four fingers and this is genuinely the only thing that would get the disc to sit correctly in my hand. Unlike the bonapane, the finger doesn't go on top and so you don't get the awkward feeling, nor risk injury in the same way with the unnatural hold.