Animating on a slope is the same as the bouncing ball. First, figure out location and key poses(Also called golden keys or extremes). I proposed a cheat by using a path to follow instead of manually keying the following of the curved surface. Second, do scale AKA add physics. This is the squash and stretch. In your case you will probably want to do this as the third part since it looks like you aren’t using a rig. Third, add rotation AKA spin. In your case you probably want to do this second. Fifth, clean up. This is where you make the adjustments to location for the squash and stretch. I skipped fourth, because it doesn’t look like you have anything that needs secondary actions like follow thru and overlap. There’s a common saying among animators: “Everything is a ball.”
